I just finished re-editing my book for about the hundredth time. I'm hoping this is the almost final one before I begin sending it out to publishers and agents. I have one last group of people reviewing it, and once they've given their edits, I'm done!
I've been working on this manuscript now for about a year and a half. Right now, it's about 71,000 words (I know this, because that's one of the things they ask you to include in your query).
Some of the things that have changed over that time:
Every character's name except the main character
I wrote it in third person, changed it to first person, then back to third
The love interests of the main character
The ages of the love interests of the main character
The death or life of the villain at the end
The identity of the villain
POV-- multiple views narrowed down to one. (By the way, I actually found it very helpful to write from multiple views first, although at the time it was an accident. When I finally wrote it just from one character's view, the other POVs helped me know what all the other characters were thinking, and why they were acting the way they were-- even though it wasn't included in the manuscript).
Hopefully, my little crew of editors don't find any blaring mistakes in this last manuscript version. Every time I make a change I literally have to comb through the entire manuscript to make sure that I tie up all the loose ends. That gets quite time consuming when the manuscript is over 200 pages.
I've also found that whenever I make a change or edit something, I have to go back at least once and re-edit my edit. Usually, I can't do this in the same day or I'll miss the problems. I have to walk away from it for a day or two so I can look at it with a fresh mind.
It never ends...