I guess it depends on how much you are making. For 300k, I'll work 75 hours a week and not burn out. The incentive is there.
If you con me into working 75 hours a week for 70k, I'll burn out when I realize I've been wasting my time propping up a loser.
I'd imagine most people are the same. Pay them enough, and they will cope with terrible conditions. Con them, and they will lose interest a lot faster.