Has the upper limit on Presidential candidate ages been hit?

[Dr. MB]

Not at all. So obviously Biden could run for another term in 2024 and he'll be 86 by the end of it. But I could also see, in the future, some even older candidates for president. The average life expectancy of a U.S. president seems to be pretty high (every one of them since Ford has reached 90 if they're not younger than that right now). Same thing for First Ladies - 6/9 of the most recent ones (who aren't younger now) have hit 90.

Electing geriatric leaders was pretty rare here until recently though but it's been going on for a while in other parts of the world. While ignoring the obvious (dictators who can't dare to give up power) you'll see examples like Mahathir Mohamad who was serving as Malaysian PM at 95. I wouldn't at all be surprised if we get a president elected for the first time over 80 pretty soon.