Does having regular case endings with one declension result in repitition?

[xBlackHeartx]

I like the case system of German, because it frees up word order so much. However, I rarely consider case for my own conlangs because I don't want to mess with the non-sense that is multiple declensions, but doing that could make sentences repetitive. I highly dislike the idea of virtually every sentence having to have an accusative marker in it (assuming nominative alignment anyway). I think it would just look stupid to have the majority of the sentences in any given text have this one adposition (or a noun with a specific ending) stuck in the middle of them.

Of course, the only case system I have extensive familiarly with is German. German doesn't have this repetition problem thanks to there being multiple declensions for nouns, and pronouns following their own irregular declensions. Of course, not all languages with case are like this. Some are perfectly happy with most sentences having a noun that ends in -t or something like that.

My question is, how repetitive do sentences end up if you have perfectly regular case endings with a singular declension?

[Linguaphile]

I like the case system of German, because it frees up word order so much. However, I rarely consider case for my own conlangs because I don't want to mess with the non-sense that is multiple declensions, but doing that could make sentences repetitive. I highly dislike the idea of virtually every sentence having to have an accusative marker in it (assuming nominative alignment anyway). I think it would just look stupid to have the majority of the sentences in any given text have this one adposition (or a noun with a specific ending) stuck in the middle of them.

Of course, the only case system I have extensive familiarly with is German. German doesn't have this repetition problem thanks to there being multiple declensions for nouns, and pronouns following their own irregular declensions. Of course, not all languages with case are like this. Some are perfectly happy with most sentences having a noun that ends in -t or something like that.

My question is, how repetitive do sentences end up if you have perfectly regular case endings with a singular declension?

I can think of several different responses to this question. First of all, whether they have case systems or not, many languages have situations in which there is a lot of repetition of word endings or entire words. Generally, I think speakers of those languages don't tend to notice the repetition much or give it much thought.
For example, English tends to repeat the word "the" a lot. (German doesn't have the same level of repetition of its definite articles precisely because of the case system and the three genders; there is a much wider variety of definite articles that can be used - der, die, das, den, dem...) In English we tend not to notice the repetition of the word "the". (For example, in your post, in your first five sentences you used the word "the" seven times. Yet it didn't seem to excessively repetitious at all. In fact, I had to have my computer's search function highlight them in order to accurately count all seven, because our brains are actually pretty used to not paying much direct attention to them, and without using the search function I skipped over one or two without realizing it even when I was actively trying to count them.)
Spanish-speakers often perceive English as having the ending "-tion" extremely frequently. Your post had only three (repetition, adposition, question); mine so far has four (question, situation, repetition, attention). Recently, I received in the mail a "matriculation-orientation registration confirmation". So yeah, in some contexts, English does use the ending -tion quite a lot.
A past-tense narrative in English is going to have words in nearly every sentence that end with -ed, minus the irregular verbs.
A paragraph describing anything plural is going to have a lot of words that in with -s. Add to that the English third-person singular ending which is also -s, and that's an awful lot of words that can end in -s in a present-tense paragraph, if the subject is third-person singular and is dealing with plural things.
In a language with adjective agreement, like Spanish, the count of plural -s is increased even more because the nouns AND adjectives will end with -s.
The thing is that we don't pay them much attention because we are used to that being the way the language works.
In other words, at least in natural languages, I don't think there's any need to avoid repetition. Fluent speakers don't consider it odd-sounding; in fact, they hardly notice it. Of course, a conlang doesn't have fluent speakers who are so accustomed to the language that they won't notice... but that's just a choice for you to make. Personally, such repetition wouldn't bother me since it's found in natural languages too.

But to address your specific question about languages with cases and regular case endings:
Estonian is a language with pretty regular case endings, so I'll use it to give you some ideas on how it deals with repetition as well as some of the features that help it to avoid some of the repetition you mentioned. For one thing, the more cases your language has, the less repetitive the endings will be because there are simply more endings to use. Estonian has fourteen cases, all of which are used regularly, and the idea that "most sentences" would have any single case ending just doesn't really apply, even though many of the cases have extremely regular forms. However, the more commonly-used cases do have various endings depending on the specific word. Nominative singular can end in just about anything, genitive singular ends in a variety of vowels, genitive plural always ends with either -de or -te, partitive plural ends in -id or -sid or a vowel (yeah I know -sid also contains -id but they are different word classes, with the -id words usually ending with -aid or -eid or -uid rather than -sid), and so on.
Also, there is no specific accusative case. Instead, the role of accusative case is filled sometimes by the nominative, sometimes the genitive, sometimes the partitive, based on the interaction between these factors: whether the object is an object of a complete or incomplete action, whether the verb is in the indicative or imperative, whether the object is singular or plural, etc. So if you want to avoid using any given case too often, one solution is to create convoluted grammar rules that prevent such repetition by requiring different cases to be used in different circumstances even though the grammatical function remains unchanged.
Having said all that, although Estonian may avoid using any particular case ending in sentence after sentence, within a sentence there is often a lot of repetition of case endings. This is because adjective agreement applies to cases as well. It's especially noticeable in lists, and most noticeable in the plural forms, since they have multiple endings strung together which are likewise repeated in lists and similar contexts. You end up with sentences like this:

Pakub gruppidele ja üksikisikutele ekskursioone ajaloolistesse lossidesse, vanadesse mõisatesse ja muudesse ilusatesse hoonetesse.
(key to colors: genitive plural (-te-/-de-), allative (-le), illative (-sse), partitive plural (-e))

The English translation of that sentence also has a repetitive ending that doesn't sound especially jarring:
"It offers groups and individuals excursions to historical castles, old manors, and other beautiful buildings."

For the Estonian sentence, you can see here the effect of the regularity of the allative and illative cases. This obviously doesn't happen to that extent in every sentence, but it does happen fairly often on a smaller scale (i.e. two or three words with the same ending). It doesn't sound bad to me. The focus really is on the meaning, not the sound, so it just "sounds right" rather than odd, just like the repetition of "the" or the ending "-s" does in English. Because it has a grammatical function, it would actually sound odd without it.

[Vlürch]

Finnish is apparently even more repetitive than Estonian, and like Linguaphile said, most of the time it's not something you pay attention to.

Rannalla olevalla kuolleella koiralla saattaa olla tuoreella paskalla kulkeva auto.
"The dead dog on the beach might have a car that runs on fresh shit."

It's a weird sentence, sure, but that's only because of what it means. It's perfectly grammatical and you wouldn't blink twice if you heard a sentence like that said out loud (unless it was this exact sentence, of course), even though it's so repetitive that if you'd made a conlang where sentences regularly turn out like that, it'd probably be seen as amateurish by some.

As for conlangs, well, that'd be entirely up to you. You could have things inflect entirely differently depending on the last consonant(s) and/or vowel(s) if you wanted. If I'm not mistaken, I think some natlangs do exactly that?

[vijayjohn]

Yeah, Malayalam also has only one declension, and I wouldn't say sentences are generally very repetitive as a result, even though reduplication (of verbs, for example) is also common. Maybe this is also in part because sometimes the kind of thing that is expressed by a preposition in English may be expressed in Malayalam using a serial verb construction, e.g. the Malayalam equivalent of 'I cut it with a knife' could probably be more literally translated as 'I cut it having put a knife'.

[OldBoring]

Yeah, Malayalam also has only one declension, and I wouldn't say sentences are generally very repetitive as a result, even though reduplication (of verbs, for example) is also common. Maybe this is also in part because sometimes the kind of thing that is expressed by a preposition in English may be expressed in Malayalam using a serial verb construction, e.g. the Malayalam equivalent of 'I cut it with a knife' could probably be more literally translated as 'I cut it having put a knife'.

I use knife cut it

[Saim]

Yeah, Malayalam also has only one declension, and I wouldn't say sentences are generally very repetitive as a result, even though reduplication (of verbs, for example) is also common. Maybe this is also in part because sometimes the kind of thing that is expressed by a preposition in English may be expressed in Malayalam using a serial verb construction, e.g. the Malayalam equivalent of 'I cut it with a knife' could probably be more literally translated as 'I cut it having put a knife'.

I use knife cut it

„我用刀切”?

[vijayjohn]

Yeah, Malayalam also has only one declension, and I wouldn't say sentences are generally very repetitive as a result, even though reduplication (of verbs, for example) is also common. Maybe this is also in part because sometimes the kind of thing that is expressed by a preposition in English may be expressed in Malayalam using a serial verb construction, e.g. the Malayalam equivalent of 'I cut it with a knife' could probably be more literally translated as 'I cut it having put a knife'.

I use knife cut it

„我用刀切”?

Or maybe 我用刀切了?

[Saim]

Or maybe 我用刀切了?

I use knife cut already. Now I’m wondering if that would be grammatical in basilectal Singlish.