Well, I finished a story in the beginning of May this year. I just looked at it again yesterday and found something kinda stupid, a minor detail, that needed tweaking.
So that's two months.
I think it depends on the person. If you have a lot of distractions in life, maybe you'll forget things in a few weeks. I think if you go back to it and find that it sounds a bit foreign, like something written by someone else, then that's probably optimal, however long that takes. In the meantime, while you wait, you can always work on something else.
A lot of writers complain about having too many ideas. The wait time before revision gives you an opportunity to research or draft something else. And it'll take your mind off your other work.
I don't do this myself. I'm just trying to be...helpful.