I think age is a bad marker to go off of as well. Different people age in different ways. My point about term limits is limiting total power a person can wield in their lifetime. As a thought experiment, consider if people could live to 300. Do you think any of the entrenched politicians would give up power after 100 years? 200? Would McConnell or Pelosi give up their positions? I can guarantee you that we would still have politicians leaving only because they died after well over 200 years in office. Democracy demands a diversity of voices. Term limits are a cheap way of getting new ones in regularly. Limits can be reasonable to ensure there is experience, but they need to be there or else we will devolve into entrenched power as the only power.

What we really need is better voters. Term limits are a hack trying to work around the voters wanting to elect the same person over and over again. No, I have no idea how you fix that.