At this point, the copy editor will be looking for typos and formatting glitches, and that's what I'll be looking for–from here on, even a small change will mean they have to reformat a bunch of stuff, and you don't get to rewrite in galleys unless you are willing to pay for the time it takes to recast the book.
Aside from piddly stuff, it had better be done by now.
I'm a few chapters into it, and so far, it's pretty clean. Any corrections I spot, I'll upload to my editor and that'll be that until I see the print copy.
Editor's note: The second ms, The Vastalimi Gambit, is officially turned in.