There are a million studies that talk about how many hours a week will get maximum productivity out of a knowledge worker. They disagree with each other. Why do some people seem to perform best on 20 hours a week, while successful startup founders can put in 100?
I could put in 16 hour days easily and stress-free if my job description was “do whatever you want.” I already do that for free whenever I can. My job is not “do whatever you want” and it never has been. But my jobs have not always been “do exactly this one thing you hate”, and that middle ground is the uncontrolled variable confounding the million studies.
If you want some people to perform better, and the question you’re asking is “how many hours a week yields maximum performance,” you’re being an idiot. They can push themselves harder if their jobs are less stressful. Go watch the movie Office Space.
Things that make peoples’ jobs easier: give suggestions instead of ultimatums, don’t make up artifical deadlines, listen to them, give them creative freedom and a sense of ownership, minimize the coordination overhead they have to do, get out of their way, don’t interrupt them, etc. This is really not news. The point is that they can work harder if you make working feel good. It’s condescending to think it’s coddling people to make their jobs easier. You’re a manager. Your job has way more creative freedom, sense of ownership, and power. That’s why you can work harder and longer.
If you think it’s unrealistic to make peoples’ jobs less painful, here’s a helpful trick you can use to brainstorm better: stop being an asshole.