I recommend Joe Friel's latest book Fast After 50. (http://www.amazon.com/Fast-After-50-.../dp/1937715264) Joe turned 70 and did a study of what he could expect regarding continued competitive racing at that age. While the book is directed towards racing fitness there is much to be learned for the more mature riders to slow the effects of ageing on performance. I don't race but I have to "train" to be able to ride with the Saturday morning club ride. BTW the book is an easy read, not overly technical like The Racers Bible or even Cycling Past 50.