How old do you think the cut off should be? What do you think the typical life expectancy is at that age? What is the typical term of government?

Tajing your example of age 80, in the USA, that would give a life expectancy of 9 years for women and 7 years for men. That’s 2 elections minimum.

Of particular note for them to vote on - health care, pensions, right to end life, hospice care, inheritance, general issues that affect their family,.