Well, I only lasted until about 1 a.m. last night, and didn't make any giant strides in that time on CBv4. My neck felt crappy and I was surprisingly tired.
But then I rationalized that the idea wasn't to stay up as late as possible to code just to say I did. Regardless of when I'd go to bed, I was still going to sleep seven or eight hours. So I resolved that if I just went to bed, I would get up and start coding in the morning.
And what do you know, I actually did. I slept for about seven hours, got up, had some breakfast, and went to it. Granted, I didn't have the greatest time since I was tracking down a problem, but work was done, and I intend to continue throughout the day. I still get the sense of accomplishment!
Oh, and the neck feels much better today. A little soreness when I move it in certain directions, but overall I have total movement. Plus the sun is shining into my office, something I don't get to see very often. It feels very good.