I think this just happens a lot with any sport that you've loved and done for a while. I've been quite the weightlifter for the last 10 years -- totally addicted for a while. Then a couple of years ago I started dragging a little -- next, I bought my road bike. I love to ride my bike and I still weight train 2 to 3 times a week, but not with quite as much enthusiasm as I used to have. I just like to keep switching things up to keep myself interested. Right now, I'm loving the cycling, so I figure whatever keeps me fit.