In some other countries other than the United States some 70 year olds and above have to retake their driving test or come in and renew their drivers license more often than those under 70 years old.
However in the United States you do not have to retake your driving test ever again as long as you live as long as you pass the eye exam and can safely drive the vehicle.
I saw a 100 year old man in the DMV before here and he took his eye test, and renewed his drivers license and I would trust his driving over some new driver that has never drove before.
He was able to walk on his own, stand on his own and had a good mind and eyesight.
It's not really the age that is a determining factor as to when someone should stop driving but instead if the person is able to actually drive safely.