My father , Bob, drove until 85 or so, but at his funeral last week (he was 97, some of you may have known him), a cousin of my mothers drove over from Burley , he is nearly 89. The DVLA reported there were over 1000 drivers over 90.
We have a friend who is 93. She gave up her licence when she was 88 because of some physical problems. When she was 90 she felt fully fit again and so took her test and passed. Drove to Dorset to visit her daughter. Handed her licence in again at 92. Doesn't need it any more. Others will drive her around.
As regards whether there should be an automatic aged at which a licence should be revoked - seems to me it should be at the age when the right to vote is revoked.
I think that an OFSTED-type inspection of the driving abilities of all drivers with, say, a random selection of 2% of motorists being inspected every year would be fun.