People have asked me when I know a story is done. There are really two questions here. One is, when am I done with a story. Two, when is the story done.
I am done with a story when it has sucked out the marrow from my bone, when my children think that I am part of the computer, when the dog has gained 10 pounds because I can't find the time to walk her, bills are late because I was too busy writing to send in the envelope, my house and dust bunnies are one, and when the thought of writing more of it puts me in a zombie frame of mind. That is when I know that it is time to take a break from the story. A break. This means handing it over to someone whom I trust to edit/critique it for me.
And then, about a month later, I feel the story pulling at my brain. Telling me where I screwed up and how to fix my messes.
When the story is done is when it is published and I can't change it even if I don't like something in it.
So, like being a mother, a story is never really done.