I agree. If I'm working on something particularly interesting, I can code for much longer for a day or even a few days and still be making useful progress. Howe

I agree. If I'm working on something particularly interesting, I can code for much longer for a day or even a few days and still be making useful progress. However, for routine grunt work over the long term, I don't think I ever sustained much more than 6 hours of productive work per day when I was programming full-time. Past that, I would start to either slow right down or make mistakes that ended up taking more time to fix later. I did find that as I started taking on other responsibilities as well as the technical stuff I could make use of the extra time for that without affecting my programming much, but I suspect if I ever move to full-time on the business side the lack of variety will be a factor again.