I just happened to stumble across a blog post elsewhere containing what I consider to be bad advice. (Hey, Alicia, maybe we should start a "Bad Advice" file. God knows it would soon rival our collection of crappy participial phrases!) I won't out the source, but the basic advice boiled down to this:
Write short sentences. If you write long sentences, you suck.
This bothers me on so many levels that it's a little hard to articulate all the ways it bothers me. Some long sentences are marvels of good writing, lucid and crisp and elegant despite the length. And some short sentences are dull beyond belief. Yet, there's a kernel of wisdom underlying the bad advice, so we can't just discard it outright.
I read somewhere -- some academic study long since lost in the mist of memory -- that readers can most easily grasp the ideas in a sentence when that sentence contains 18 or fewer words. I don't remember much else about that paper. There was some discussion of methodology (not every 18-word sentence is built alike), but I can't remember the specifics. What sticks with me is that number, 18, and some of the reasoning behind it. Most sentences run around 5 to 15 words long. There is a vanishing point on the low end, but a long sentence can become even longer, and longer still, without ever hitting a similar vanishing point. There's simply no limit to how long a sentence can be. In fact, in school, we did writing exercises that required us to write super-long sentences of 250 or more words. Those were fun, challenging exercises that I hope to never do again. ;)
So, why 18 words? It's nothing to do, as I recall, with how the specific sentences are written. It is just that we're used to something shorter. If most sentences are 5-15 words, then most readers are acclimated to grasping sentences around that length. An extra 3 words on the top end probably wouldn't make much difference -- an extra adjective here or there, maybe another prepositional phrase, but really, another three words likely won't add much more weight to a sentence.
Yet, there are plenty of writers generating long, languid, highly lucid sentence with scads more than 18 words. Jhumpa Lahiri comes to mind. She writes beautiful sentences, and many of them are long chains of clauses in a series. You might have some favorite writers of long sentences, too. These writers demonstrate that sentence length is not a barrier to reader comprehension, to good storytelling, or to writing quality.
What is important is that long sentences be clear. That's the rub. It's not that a long sentence is per se bad. It's just that they provide more opportunities for confusion. But if you can generate a clear, strong, ultra-long sentence, then don't hold back just because there's a bias toward short sentences. It might be just what you need in that spot of the manuscript to add a perfect grace note, no matter how the academics count the words.