I did 80+ hours per week for years in medical school, residency, and fellowship. Many people in medicine make a career of it. It's not as unusual as you think. There is certainly a fair argument to be made that it's not particularly healthy or a good idea, but I can assure you that for some people it's quite sustainable.

> I did 80+ hours per week for years in medical school, residency, and fellowship. Many people in medicine make a career of it. It's not as unusual as you think.

Possibly a bad example; in most developed countries the medical professions have amongst the highest rates of depression, suicide and divorce.

Good point. And if you look at the folks working in banking and management consulting, they'd laugh at the concept of a 9-5. 80+ hours / week is not that much of an outlier.

The key word of your post is "sustain". You may be doing it now, but the cost of the 16 hour days is going to take it's toll.

Doable if you don't have a family or care to hang out with friends. The key is really to work with your friends so work doesn't feel like work.

There's also significant variation (apparently biological) in how much sleep per night people need. If you're one of the people who can get by fine with 5 hrs/night of sleep, you have almost 20% more awake time over someone who needs 8 hrs/night to maintain the same alertness.

(You can also try to modify it via caffeine or other drugs. I'm not sure I'd recommend it, but apparently many of the people historically known for their superhuman workhours were heavy amphetamine users--- Winston Churchill, Ayn Rand, Paul Erdős.)