If MS had been declared healthy, would his age have placed him at a disadvantage? What is the level of fitness needed to go the distance in an F-1 car? Or maybe it is more about reflex and reaction times?
I don't think it would have been an issue for Michael at all. The reflexes might become a bit of an issue into his 40's, but the only time reflexes really come into play is if you have to save the car or get out of the way of an object or something. I would GUESS that Michael could carry on for a few more years is he really wanted to. Mansell wasn't very fit at all but he managed to win into his 40's and I think Jacques Lazier was in F1 until he was 44 or 45.
Fangio won his first title at 40 and his fifth at 47. After the whooping he laid down on Mike Hawthorne and Peter Collins at the Nurburgring (at 47 years old) there was no doubt that age was not the factor. Yes the cars are faster and more physically demanding however there is no reason someone cannot be both mentally and physically fit enough to be World Champion well into their 40's. Schumacher could definatly do it again. The problem lays in motivation and drive. This comes from within and unfortunatly too many people 'age' too fast and mentally give up or quit even though the body is fine. Some people loose motivation in their 20's (I know people this age who are already old men) and then there are people like my grandfather who was sharp and motivated right up to 102 (the body at this stage was no longer ready for F1)
There are tons of fighter pilots in their 40s and 50s (my cousin was one of them). The training these pilots go through daily is easily equivalent or equal to that of a F1 driver.
Have a look at the TOP GUN head fighter pilot trainer. The guy is nearing 60 yet he kicks these young punks around at 50,000 feet all day long.