text: Bodies are pretty resilient.  That said, I'm sure it's NOT good for someone to work non-stop without a break.\n\nYoung people are hired for 'brain' work as you put it because they are fresh out of school and on the cutting edge of technology.  Older people (SOME not all) prefer not to learn new things and are then relegated to accepting what positions they can to make a living.\n\nJust my opinion.