Maybe we just need a mental competency exam of some kind... Like, I think Bernie is still thinking pretty clearly, but Trump, Boebert and Greene? Literally mentally ill... And not just to pick on Republicans; Biden is clearly senile, Clinton is clearly a sociopath

There is no necessary correlation. Everything you are saying is representative of today, but not universally true. That's my point.

It would be identical to say that a certain skin color is strongly correlated with high imprisonment and low economic status, so therefore we should ban certain skin tones from running for office. Those correlations may be true today, but there are reasons that have nothing to do with the actual skin color that make it the case. Similarly, there is nothing about the number of times you've gone around the sun, or the length of time you've been alive that necessitates your cognitive faculties to degrade.

There won't be a scientific breakthrough that doubles the average lifespan of every human on earth. There are so many flaws with this idea it's exhausting just to think about it.

But there will continue to be scientific advancements that extend our life expectancy by a small bit every year, for an indeterminate amount of time. Which is why raw "age" is not a good measurement to use.

The basis for everything I'm saying is that age is a protected class in the US, which is why forced retirement in general is illegal.

Yes, there are many instances where institutions get away with it anyway, but as the AARP puts it:

Numerous scientific and medical studies find no need for this age-based discrimination.