I agree with most of what TTT says, but I don't think age is completely irrelevant. The longer you drive the more experience you gain and that should contribute to safer driving. I am not a hundred but fall in to the elderly group, consequently my eyesight and hearing is tested yearly so really all that is in question is my reflex action. After a few days of driving I'm quite happy with that as it was tested three times in one day in emergency stops because of people, young and old, driving out of side roads without stopping and in one case I noticed, without even looking.
So, no I don't think they should be automatically banned based solely on age, but retesting should be considered at some stage.