Simple, if you can't get elected before a age X then you shouldn't be able to get elected after (life expectancy - X)
Example: Can't become president before 35? Life expectancy is 75 for men and 80 for women, men can't become president after 40, women after 45.
Just watch how fast life improves in the USA if you put a measure like that in place, not just from having younger politicians but also from wanting to be able to get elected later in life.
Same for voting right, can't vote before 18, can't vote after 57 and 62.