You'd be surprised. I can think of 2 docs in my current group that are literally over 70 and working as FTEs. One of them has to work 7 overnights this month and swings to days then back to nights over the course of 2 weeks. The other guy freely admits that he doesn't have enough saved due to a divorce and "giving it all away to my kids", etc.. One doc from my old group...we had to pull him off the schedule at 75 because his health was just failing and he started not showing up for shifts or could barely make it through one. He had several divorces. Divorce without a prenup is probably the number one threat to any physician or high earner unless they are married to a spouse with commensurate earning potential.
Another thing I've noticed during my career are so many docs that think they are just as good at business vs practicing medicine. Half blow up their savings on a bad business venture. Half end up pulling it off.
What's got me mystified are the new grads who are increasingly scaling back right out of residency working 0.8/0.6FTE, etc.. Most say they are "burned out" right out of residency or seem less interested in money/savings and more interested in quality of life. All that is perfectly fine of course but I'm not sure how things will turn out for them because if they are truly burned out, how do they expect to work a full career? (Which they will no doubt have to do since they are only working 0.8FTE). Then you factor in the lost savings from working hard those first few years out and piling it away for compounding.