There doesn't seem to be much of a relationship between numerical age and performance.... I can remember one of the ancestors, cattleman all his life, cutting out scrubbers in his eighties, tooling through the trees and over the rocks at a hundred miles an hour, horse full stretch, stockwhip cracking, sweat flying, dust and sparks, all action.... Some people, on the other hand, seem to start tripping over things when they hit fifity. Some don't get that far.
My impression, just looking at these older guys, is that if they are fit enough to want to go to work, then they very probably are fit enough to do it.
Seems the Australians and the New Zealanders, yet again, have got it right.