I don't agree with this. Why not be able to have a startup succeed with 7.5 hour days?

For me, I can put in a day longer than that when I need to, in an extreme circumstance. But if it becomes often, I just can't be productive longer than that. I loses ability to focus, and start accumulating burn out. My throughput is greater at 7.5 hour days than 10 hour days.

Of course, if there's like a week leading up to a launch where you need to crunch, that's different. I've been there, and have been able to be super productive like that for a week. But it can't be sustained... I feel like I'm basically borrowing some productivity from the future, and that debt will catch up to me eventually.