An important factor is not long hours or overwork, but how much control one has over one's work. Can't quite find it now, but there was a study which found that

An important factor is not long hours or overwork, but how much control one has over one's work. Can't quite find it now, but there was a study which found that senior ranking people had better health outcomes than junior folks, even though both sets put in the same number of (high) hours, because the senior people had more agency over their work. I doubt Musk saw 100 hr weeks as soul-draining drudgery where he needed to run out the clock.