I just finished my final edit of book IV. I haven't slept in a month. I'm up all night either writing or thinking. Who ever thought a book was done when you write the last page? I rewrote 59 out of 61 chapters, from beginning to end. My editor was ruthless (in a good way), and that was the best thing that ever happened to the book.
The one thing that I realized though is that I'm never satisfied. I feel great when I finish a chapter and make all the changes, do all the rethinking and end up with something exciting and well written. But then I go back later and I start all over again. The process never ends.
Thank god for deadlines. Once they come, the book is done.
My editor's doing the final line edit now.