Interesting thread, in spite of some of the silliness. There is some danger in comparing airplane pilots (specifically excluding helicopter pilots) with car drivers. The required knowledge is different, and the usefulness of "fast" reflexes is different. The car driver issue could easily be taken care of with driving simulators and real testing. The driving test in the US is a joke. I am for retesting on a regular basis... of all drivers. I have reached an age where when I complain about an old ____ driver, my wife frequently chimes in with, "I bet he/she is younger than you."
There are many reasons for poor performance in both driving and flying. Lack of practice, not stretching during that practice, I suspect are a big part of it. Some of those bad old drivers were once bad young drivers. Airplane pilots don't need super fast reflexes. They do need good judgement and basic skills. None of the recent 121 stupid pilot tricks were with pilots in their 70s, much less 80s. Asiana, AF, Colgan, the commuter at Lex, ...
It would be nice if BFRs were better at weeding out a lack of basic skills, but hey, some of those CFIs don't have them either. I personally don't think there is an age that works particularly well. I know a family with 5 living siblings and three have Alzheimer's. Of the three that do, NONE have reached 60 yet. One no longer functions normally, two are getting worse quickly. Really sad, but is 50 something therefore the right age to take away the medical?
It has to remain performance based not age based. If BFRs and medicals aren't working fix them, but trying to set a specific age never will.