Considering his net worth and the rules and values how he lives his life, I would certainly count warren Buffet as mustachian. Go back and look at mmm rules for living, and then look how warren Buffet loves. The only thing he hasn't done is retire early but that's an optional step.
I get that he loves working. But he's certainly not optimized the health part of life... Nor the environmental impact (no one who has their own jet plane has, regardless of how useful it is and how much money you have).
I wouldn't assume this. A lot of extremely powerful people have a really excellent work-life balance because they have extremely successful/powerful/competent people below them to take care of the vast majority of day-to-day tasks.
When you're at the very, very top of an Empire and you have a really functional hierarchy, you're essentially just a final decision maker for critical issues. You stay briefed on things, but typically you won't even hear about a problem, even a major problem, until the person you trust beneath you had already solved it, or they're coming to you for final approval on the solution they've already come up with.
I've spent quite a bit of time with billionaires and the ones I've known have had pretty amazing work-life balance and virtually no one has access to them even in emergencies. An emergency has to make its way through a giant pyramid of perfectly capable problem solvers to even get to the top, and by the time it does, their briefing can usually wait until regular business hours the next day.
It's the junior and mid-level executives who are burdened by the insane demands of running companies, not the top, top brass.
Now, if the business doesn't have a solid hierarchy, the top brass are control freaks who refuse to effectively delegate, then they'll have to do TONS of management labour, which definitely happens quite often.
But given the way Buffet does business, I wouldn't be surprised if his work-life balance is excellent, and continuing to work is just what he enjoys as part of his overall best life.
A quick google says that he never works late, always gets home at the same time every evening, and heavily prioritizes work-life balance.
I saw this up close in my family on a much smaller scale. My aunt was the president of a major multinational corporation, and I remember in the 90s/2000s assuming that she probably worked crazy long hours and was constantly having to be available to her work. I assumed this because my mom was an executive for a large national corporation at the time and worked like a dog, so I assumed her sister must work that much harder since she made over 20 times as much as my mom.
But no, she had put in her time as a corporate slave to get to her position, but once she was well-ensconced and seen as essential, like Buffet, she never once got home late. Ever. For decades. She didn't have to, she had people for that.
So Buffet may be making essentially zero sacrifices in terms of his health and well-being by continuing to work. You have to fill your time with *something* and there's nothing inherently unhealthy about filling it with work if that works for you.
My health is my #1 priority, and I have no intention of ever retiring. It helps that I'm the top of the pyramid at my company, so I determine exactly what my work is like. Granted, I'm also the bottom of the pyramid at my company because it's *just* me, so I probably have to deal with more bullshit than Buffet does, lol.