I don't like re-writes and only do them because it's absolutely nessesary, so I'm coming at this from the other side from where you are. I've heard about famous writers who have produced amazing works by editing them over and over for years. It's the perfectionist versus, well, whatever the opposite is. I'm jealous that you can do it, but I have tremendous sympathy that you feel you need to re-write over and over. I think it's a battle with yourself after a certain point, and not about fixing the work anymore. I've fought with myself plenty and I know how hard that battle can be. After a certain point, just publish it. I know thats incredibly hard to do but at some point, no matter how bad you think it is, finish it. Publish. Move on. I mean, be logical about it, but give yourself a break and allow it to be done.
I did some acting for a movie 10 years ago and the director just keeps tinkering with the movie. He still hasn't released it yet. It's going to be a B rated movie no matter what but I feel like he is determined that if he tinkers with it enough something magical will appear. He hasn't done any more filming that I know about and I feel like his career stopped when he started that film. I don't know if this rant helps or not. Some of the greatest works have come out of a long period of editing. Lord of the Rings took 10 years. So perhaps 10 years is reasonable to brew a book. (Yet another reason not to tie your book to a date too hard.) But it has to be finished at some point.
Good luck with yours,
- Mark Charke