One friend of mine essentially refused to take breaks after school. He'd get home and immediately start working on the day's homework. It would frequently take him until after 9 o'clock to finish up work that shouldn't have taken anywhere near that long. I know he's an intelligent fellow, and not prone to distraction. He'd just get stuck.

I'm /certain/ taking a break would have gotten him into a fresh mindset, and let him finish it all up faster. And, if I had /not/ put some hours between getting home and doing my homework, that it really could have taken me many hours to finish.

Just one speculative data point, but there it is.