I was chatting with one of the shop personnel about the possibility of having to replace the gears. Bike parts wear out with time and use, and I've put over 12,000 miles on that bike in a little over three and a half years.
Maybe it's time to dream of a new road bike? We even brought up the possibility that the bicycle itself will wear out. If it does, I'll shop around for something a few pounds lighter. I'll likely want to get lighter pedals, and may end up with (gulp!) ROAD BIKE shoes instead of MTB shoes. That will mean being a lot more careful about how I put down my foot when stopping (heel first!) so it doesn't slip out from under me. That's a scary thought.
The expense is scary, too. Getting a new road bike will mean spending several thousand dollars, no small amount for me. On the upside, if I do buy a new road bike, the old one can be my guinea pig, so I can learn more about doing my own repairs/maintenance. Maybe I can even learn to replace the chain myself!