staehpj1

It depends on what level of training/performance you are talking about. You are kidding yourself if you think your absolute top end potential doesn't decline at a much younger age. Look at pro racers, how many do you see over 40 that are not declining?

That said, you can maintain a pretty high level of performance and certainly ride a lot of mileage into very advanced age. I felt some fairly significant changes at 45 when it came to my maximum performance. I had to work harder to get to a given level and didn't have the same edge, but I still could do long miles and can today at 72. I lately I mostly ride MTB (daily) and still ride fairly challenging trails. I rode my first coast to coast tour at 56 and still could do another at my current age. I'd like to think that barring some major health problem I could do another one 10 years from now, but we don't get any guarantees for the future.

One thing that helps a lot is that these days injuries that would be the end of a riding career and be fixed with surgery. Thus far I have avoided knee and hip surgery though.

Edit to note: I don't buy the "must spin high cadence" to save knees orthodoxy folks preach. I have always used a variety of cadences for a variety of conditions. Buddys always said my knees would be shot at an early age. At 72 my knees are still intact after a huge number of miles on and off the road.