Putting politics aside … Why don’t they have an age limit on the president (or any elected office)? E.g., you must be younger than the average life expectancy (currently men: 73yo / female: 79) - while in office. https://www.ssa.gov/oact/STATS/table4c6.html
The same reason we don't have a race or sex limit on the Presidency. We should only have competency limits regardless of any other factors. My grandfather died at 101. He was extremely sharp until he was 98 and on no medication. I'd vote for that 95 year-old over either of our current choices without hesitation.
All these anecdotal superhuman tales fail the smell test.
There is this hyped longitudinal study, but it doesn't say what roles these "superagers" were in, only that they had slightly better cognitive outcomes than their peers.
No one has cognitive capacity or neuronal volume of a 35 year old at 65, not to speak of 95.
It is delusional to think anyone can escape the effects of aging at this point in time.