I think a lot of the discussion that goes into these "I ain't what I used to be" laments is just a matter of perception. The fact is as we age, our bodies decline. That's just basic biology. At 72 y/o, I can't do what I did when I was 20 years younger without feeling it more and taking longer to recover. So what? I still love the feel of riding, pushing myself hard enough to see little improvements over time, but not so hard I miss the scenery or that lovely sound a good set of tubulars makes on a hard climb or in a tight corner on an enthusiastic descent. To me, it all depends on your perspective. I'm either a very average 50 y/o or I'm in the top 15% of what's expected for a septuagenarian. Either way, my body still responds to training. Just not as fast or as much. But it feels just a good as when I was a whole lot younger, and it makes me smile just as much now as it did then.