I'm going to be as succinct as I can, because that was a sort of tripartite question.
First, I don't think using sentence length as a proxy for the need for a prelim is appropriate. They're two different questions. You're saying, “Here is an apple; what does that tell us about oranges?” It will not help, so I don't think that's helpful.
I can't remember what the second one was, but the third one—