I like to think I can program more than 3-4 hours a day sustainably, I know I've had days where I worked for 8 hours (although its not always pure programming)

I like to think I can program more than 3-4 hours a day sustainably, I know I've had days where I worked for 8 hours (although its not always pure programming) and then came home and worked for hours more on personal projects, or also worked on the weekend on a personal project for many hours. The thing is though that I have a habit of distracting myself fairly often by going on here to read articles, Reddit, etc, I'd say I normally wouldn't go more than half an hour without some forced distraction, often times even more often that that. I think doing something like this can help to keep you mentally fresh, at least it seems to work for me