People sometimes ask me how long I spend editing these things.  Not much.  A cursory glance, a few changed words, and then it's done.  I tend to call my drafts "finished," which isn't really accurate, because I'll find myself going back over them days later, changing little things here and there, even if no one will ever read the edited version.  So, I guess the answer is that I write it out and then I'm done with it, but I don't ever stop thinking about it, and I don't ever stop trying to improve it.  Whatever it is.