I believe that I could edit eternally, and I have to be very stern with myself about it. I edit in layers, so for example, I might start editing for character, checking to be sure I've been consistent and interesting and all that. But then I see a phrase that isn't quite the way I'd like it, and pretty soon I'm editing something else entirely.
Now that's not all bad, because it probably will improve the piece, but WHERE does it STOP? Maybe when I'm so sick of the whole thing that I can't stand to read it one more time. That doesn't mean it's how I really want it; it just means I've made myself accept that edit # 30 or #50 or whatever is the final one. And this time, I really mean it!