Same here, but my definition of "fun" has changed over the years. When I was a teenager and in my 20's, my idea of "fun" was what many of the 50+ riders do - just riding around, looking at everything from a new perspective, and hardly raising a sweat.

After buying a new mtn. bike to ride with my daughter's swim team excursions in my early 50's, I quickly progressed to a better mountain bike, a road bike, a better road bike, a better road bike, etc. I found out that what was "fun" to me was constantly improving my strength on a bike.

I'll always remember the day I saw a couple of riders pass me and just fly up a hill. I thought - they look like gazelles. Totally effortless movement and beauty of form. After that day, all of my efforts were to be the gazelle.

After a number of intervening incidents, both good and bad, over the last couple of years, I'm still riding a little, but now I'm trying to be a gazelle when hiking the mountain trails of northern New Mexico. It's working pretty good so far. I still have fun on every ride and every hike.