My wife and I have discussed similar topics to this frequently, and I agree with kwin's view "I support the manditory retesting of all drivers every 5 years"
Let's face it - you're in control of a potentially lethal device, and in my mind it would be comforting to think that people could handle it safely, regardless of age. Yeah - it would be stressful, an inconvenience, and costly.. but if it made you more aware and a safer driver, then it would be worth the cost IMO.
I often wonder if I'd pass again first time !
Bull!