Not sure what that age should be, but I'm thinking the testing should start at 60-65 and probably be done every 2-3 years after that. My wife and I are approaching that now, and I can see her having more problems with sight and timidity, particularly at night. I know I'm not at fast on the reflexes as I once was, but I balance that with caution (situational awareness, slowing in advance, staying away from other obvious idiot drivers, etc.).
I watched our parents age and slowly lose their abilities, with my father-in-law getting killed when he yanked across traffic without a clear view (a wait of 5-10 seconds would have saved him).
I would rather collapse my world and live without driving than put my kids through the hell that accident caused...
Agreed!!