I don't believe that this should ever go to zero. I think the heart of this question is : how do you maximize long term productivity? For me, if I work more tha

I don't believe that this should ever go to zero. I think the heart of this question is : how do you maximize long term productivity? For me, if I work more than 70-77 hours a week for an extended period, my productivity drops. I can flirt with 90 hours in a pinch, but once I break 70 hours I start to make mistakes. I don't know about you, but my experience in writing software is that it is like poker in the sense that a single mistake can end up costing a lot. So, that translates to an optimal 10-11 hours a day with an occasional 12 hour day. This leaves 5-7 hours of free time per day. I also believe that a balanced mind, body and emotions leads to better results than overemphasizing one or the other. So, I focus on exercising to keep a sound body, sleeping 7-8 hours per night and spending an hour or two relaxing every day. Of course, I'm not rich yet, either.