80 years old, 90 hours a week, ok.

I know, to each their own, right? It's earned him a net worth north of a billion dollars, but for him it clearly has nothing to do with the money. He does not really spend much of it at all, he just works. It's like OCD.

I've seen first-hand that it can become a self-reinforcing problem and solution in one. You spend too much time at work and never develop meaningful personal relationships with your spouse and children. Years later, when most people retire to spend time with the spouse and children (and grandchildren), there's something missing, and the solution is to head back to work, where there can be more substantial professional relationships (and room for denial about the personal side).

Or, maybe they just liked their job.

Reminds me of the recent HN story about the lady who ran a large furniture retail outlet in Nebraska. She was something like 85 years old when Berkshire Hathaway bought the company. It never occurred to Warren Buffett to demand a noncompete agreement from an 85-year-old, but he says he won't make that mistake again.

Maybe he has nothing else he wants to do.

And if so, that's OK.