I'll let you know when I finish it.
Seriously. I'm on the 20th+/- draft, and 6th or 7th total rewrite. But keep in mind that this started as one book, and now has sort of expanded itself into a five-book series, so much of what I had written already will be saved for future books, much will go in the "WTF was I thinking" file, and much had to be written from scratch as a new foundation. So yours may be very different.
If you're a perfectionist like me, you may never feel it's quite "done," but at some point you will have to let others read it. I suggest you do that while it's still in what I call the "baking period." You reach a point where you can't stand to see the MS anymore, then you let your betas have it for a month or two. Then, they will come back with suggestions, and you will have had time away from it.
Just please promise that in all your editing and rewrites, you won't throw anything away . . .