Dry climate, heavy trains, and steep grades will chew them up. In the over all scheme of things, they are pretty inexpensive compared to many other things in this hobby.
Keep a supply on hand, and once you've changed them a few times, it's pretty easy. Do you want to pull 8 cars or 20? Until we start filling our engines with smoke fluid and sand, I don't see the tires going away any time soon... if ever. I don't want sand all over my layout 
unless it's glued down.
The 2R guys don't have rubber tires usually, and ask them about running big trains. Just like real trains, the bigger your train, the more engines you need to pull it. 1 3R engine that will pull 20-30 cars, needs 2-3 engines in 2R with no tires.
