We aren't really talking about overtime though, which also exists in the US, but the amount of output during a normal 8 hour day. You might get paid somewhat more than a peer for putting out 2x the output but there are massive diminishing returns.
What I was responding to literally talked about "work hours increase". I don't see how you can have "work hours increase" and simultaneously keep the same "normal 8 hour day". That sounds contradictory to me.
Even for salaried employees it is not rational to work too hard. You may spend 8 hours at work but you don't spend every minute of that time actually working. You could optimize that if you wanted but you're not going to be rewarded proportionally if at all. Returns diminish quickly and that's if your efforts are even noticed. Burning oneself out to finish something quickly can even backfire since managers can always just find more work that needs to be done.
