I have a rule which I've been forgetting lately: no programming after 9 pm. This is my equivalent of the extreme programming 40 hours a week rule. I'm old enough and secure enough to admit that I'm useless as a coder after seven pm. I can still do decent pixel tweaking and whatnot for a bunch of hours after that, but if I haven't found a bug by seven pm, I'm not going to find it that night.
Some of my co-workers at Laszlo work insane amounts (fer instance, Scott Evans' domain name is antisleep.com) and I've been trying to be like them... even turning up at work before 9 am a few times! but no. I need eight hours of sleep a night; I really truly do. Stopping programming by 9 pm is one of the best ways for me to maintain my happiness and well-being, not to mention my code quality.
In my world, schedules matter on the order of days and weeks, not hours and minutes. If our process is running at light-speed, it takes minimum a day for a code change to go from "it works on my machine" to "it's live." At a more normal speed, we do weekly or semi-weekly builds. So, reminder to self: go to sleep! Now! And eat a sandwich!