I do not care for the heroic couplet.
It’s fine for a short poem or sonnet, but when you stack one atop the other for stanza after stanza, it gets predictable, monotonous, and boring. It’s why A Midsummer Night’s Dream is my least favorite of Shakespeare’s plays, as a huge portion of it is written in heroic couplets.
What does this have to do with writing prose? Plenty.
Just as classical poetry has rhythm and meter, so can prose. Consider the following paragraph…
He had to go to the grocer’s. He needed some things for dinner. She was coming over at eight. He didn’t have much time.
Not sparkling, I know, but it makes the point that prose has rhythm, too. In this case, each sentence has about three “beats,” each starts with a pronoun, and each is constructed with a basic subject/verb/object syntax.
Prose has a rhythm, and just as with the heroic couplet, if it doesn’t vary, the prose becomes flat, predictable, and uninteresting.
This doesn’t mean that short, choppy sentences are bad, no, but if that’s all you have then yes, it’s bad. Similarly, having nothing but long, tortuous, paragraph-length sentences (unless you’re trying to emulate Proust) isn’t great, either. Action sequences generally employ short sentences, but not only short sentences. Likewise, descriptive sections generally have longer sentences, but not only those. Mixing lengths is like adding syncopation to music; it wakes up the ear and keeps the reader interested.
If all the sentences in a section of prose are all of the same type–long, short, syntactically similar, rhythmically similar–the monotony will quickly affect the reader. Keep it up for a page or more, and your going to lose them entirely.
When I’m writing, it’s almost impossible to notice these sections, so I don’t even try, but when I’m editing they become glaringly obvious. If I find myself skipping ahead, my sentences are too short. If I find myself having to re-read a sentence, I know it’s either ill-wrought or too convoluted. I make margin notes like “choppy” or “awkward” or “tighten up” to remind me what is needed.
Editing echoes help me here, too. If a name or pronoun crops up in successive sentences, my syntax is probably repetitive and bears inspection. “Echo” is my margin note for these, with the offending word circled in the text.
As with All Things Writerly, there is no rule. Repetition, on its own, isn’t bad and when employed properly, it can be a powerful stylistic and rhetorical tool. But as with Most Things Writerly, be aware of it. If you use it, use it on purpose.