[tinco]

Pulling an all nighter every once in a while, or even a couple consecutive days during crunch time is not the same as working 20 hours per day. So unless you've got a specific quote from either of them I call bullshit.

That said, Bill Gates definitely said he and some of his crew were working 16 hour days delivering their first DOS release.

Point is, you might work some intense stretches, and doing that shows your passion and might land give you an edge when you need it. But you don't need to go insane. If you work 8 hours day job, don't spend hours in commute, you can be perfectly healthy spending 2 hours of your night time each day working a side gig.

[frankbyte]

“There were times when, some weeks ... I haven’t counted exactly, but I would just sort of sleep for a few hours, work, sleep for a few hours, work, seven days a week. Some of those days must have been 120 hours or something nutty.”

Now, Musk said he is “down to 80 or 90” hours of work per week and “it’s pretty manageable.”

https://www.cnbc.com/2018/11/05/elon-musk-on-working-120-hou...

That's the quickest I could find. But yeah, I suppose 20-23h constantly long-term would not be doable. Point is though that many people can and do work even long-term the equavalent of 2 "full-time jobs".