I edit A LOT as I go. I reread my own writing constantly. I never write short stories or poetry, only novels, and I don't write that often anymore, so I haven't finished even a first draft in years. Therefore I don't really know how many drafts I would go through. In the past I've usually realized how crappy whatever I wrote was so I don't bother to redo it because it's probably beyond repair. For the last thing I wrote I started a second draft, but then I must have deleted it or something. (I go on deleting sprees. If I had every piece of writing I'd ever started there would probably be hundreds of documents, but as it is there are, I think, four.)
Within the past year or so I started a second draft for what is currently my main project, despite the fact that I hadn't actually finished the first one (it was long enough; it's an upper middle grade novel and it was 186 pages, but probably only about two thirds done). I just realized there were a bunch of additions and such that I wanted to make and I might as well start the second draft now.
I remember in school sometimes they'd make us do second drafts for essays and such, and there was never anything I wanted to change. Eventually I started purposely inserting grammatical or spelling errors in the first drafts in order to have something to change.
