SF fans and science nerds generally ought to be familiar with the concept of time dilation, where the closer you get to the speed of light the more time slows down for you subjectively. You emerge from your space capsule after a few months to discover decades have gone by on Earth, and Nirvana and Faith No More are now on "classic rock" stations. The hell.
I'm noticing a similar time-dilation phenomenon with my novel manuscripts. No, not the inexplicable presence of Faith No More (that said, Angel Dust is a MASSIVELY underappreciated disc; everyone was just pissed because they didn't get another "Epic" and Mike Patton turned out to be sublimely weirder than anyone could have guessed). More like, the closer I get to the end of the book, the longer it seems to take to produce anything. I must be within 10,000-15,000 words of the end of Always Outnumbered, Never Outgunned, if even that much, and it feels like a single sentence takes me about three weeks of typing.
Some of this, I'm sure, stems from the way authors (me definitely included) tend to second-guess the goings-on at the climax of a story far more intensely than they do the goings-on at any other point in the story. This is why the endings of movies are often reshot: when you put the whole thing together, you sometimes realize the ending you have just doesn't support the story you've been advancing. Rogue One was apparently like this. From what I understand the reshoots made it into a significantly better movie, one that was willing to project its vision through to the bittersweet end.
When I'm trying to write an ending, every little detail in that ending feels like it has to support the story I've been trying to tell. So I second-guess, I micromanage, I hem and haw and hesitate. It's not something I can push off to another draft; I want to get it right the first time and slam the door on it and move on. It's that much less I have to fix next time around.
The perfect is the enemy of the good, or so goes a saying that many people throw around thoughtlessly. What it means in creative terms, I've learned, is that you have to find for yourself the point when any further attempts at improvement are meaningless. Ending this first draft didn't require me to hit perfection, but it did require me to toss out many of the least worst options, and to recognize how, this time around, there's a ceiling to how good things can possibly get.
Sum of comment: I expect to finish the first draft by the end of June. I expect to be finished with this whole thing by Christmas. I can't say Christmas of what year, though.
If you want a book that'll get time to slow down for you in a fun way, check out my (new!) novel Welcome To The Fold, and showing your support for it by registering at Inkshares and adding the book to your "Follow" list! Failing that, you can always buy one of my existing books, available on Amazon Kindle and in dead-tree format.