Personally, I can't concentrate on doing development for eight straight hours. My focus doesn't fit in a neat box like that. Some days I'm burnt at four hours

Personally, I can't concentrate on doing development for eight straight hours. My focus doesn't fit in a neat box like that. Some days I'm burnt at four hours (but I might have had superhuman output during that time) and other days I can do marathons of crazy focus for longer than eight hours.