Nothing is good if you overdo it. I read about water as well so why not sleeping. There should be a line to draw but i honestly believe it depends on many factors and that we should sleep as much as we feel the need. if you had a two day shift at work and a day off after it is unlikely you will sleep 7 hours. I understand it maybe should be like this but in a perfect world where you get the treatment of a human. I was working in a hotel kitchen day in and day out. On my work day i get up in 6, start working an 7 am and sometimes finish in 3 or 4 am. So, i arrive home at 5 am and fall asleep around 6 or 6 :30 which means i was up 24 hours straight. I could get up in 7 hours but 10 hours was just about right for me. And the job was hard stuff.