I'm now into the latter half of my fifties (younger than most posting in this thread). I used to be intensely competitive, but ended up with permanent heart damage by training through a serious episode of the flu at age 41. That heart damage lopped about 20% right off the top of my VO2 max and ended my racing. I no longer compete with anyone other than my own age-related PRs, and now I am even questioning the wisdom of that recently as I'm finding that I need longer recovery between hard rides than I needed even a few years ago, and am having trouble sleeping after hard rides. I think everyone needs to find their own level of satisfaction and be realistic about what's good for them. It's now a well known fact that extended endurance exercise in competitive masters athletes leads to significantly higher rates of a-fib and other heart rhythm abnormalities, so one should be clear-eyed about the risks of putting in big training weeks year after year. I'm learning more and more to stop and smell the flowers when riding, so to speak.