Good question --

I can tell it's time to leave the words alone when:

1) I can't stand looking at the story/chapter any longer
2) A change I made yesterday I go back to today and change it back to the way it was yesterday.
3) I've addressed any questions my critiquer(s) have brought up, either in the text itself, or at least in my head.
4) I'm no longer excited by the words and want to move on!

Anyone else do something similar?