That's why we have physicals and biannual flight reviews. To determine if
we
are fit to fly. Flunk either one and you're grounded. Much more
appropriate
than an arbitrary limit. Heaven knows that getting some arbitrary,
government mandated limit changed would be darned near impossible.

I can see it now... Someone discovers the fountain of youth and provides
the magic elixir to the world's entire population. It freezes their
physical
abilities at 30 years of age, and enables them to continue improving their
mental function until whatever untimely accident or illness ends their
life.
There could be millions of 100 plus year olds who are in the shape of a
30
year old with many times the knowledge, life experience, and mental
ability.
Unfortunately, none of them could be airline pilots due to the Age 60
rule...

You've summed it up rather well.