After writing a pretty decent stack of accident reports at work I've long believed that EVERYONE, not just older drivers, should be retested every four years or so. There is a reason pilots have to take check rides to maintain certification; why should drivers be held to a lesser standard? When an unsafe driver kills someone, is the victim any less dead? Do their friends and relatives grieve any less? It's more tradition than anything else. That and people just don't want to take the time.
There are plenty of idiots on the road as it is and most of them are well under 70, at least in my experience. So I'd like to see it that when a driver's license expires after four or five years or so, everyone has to take the whole driver's test all over again. You think you're a great driver? Great, then you won't have any trouble at all passing the test.
And most driver's tests in the U.S. are a joke anyway. For my driver's test I had to pass a simple multiple-choice test and drive around the block without crashing, and that was in 1966. I haven't been tested since by that state or any state, just my employer, who had much higher standards including skid training. Germany for example takes driving seriously and I think it'd be great if the rest of the world adopted their standards.