Well, I myself wouldn't worry. Touchscreens have been around for a long time, and they've made them pretty durable. The only long-term experience I have with one on a remote, however, is with the Sony RM-AV2000 and even then only for about 9 months, but so far so good. It's a different type of touchscreen, though (if you look in the right light you can actually see physical "squares" that correspond to the LCD buttons).

The Pronto, on the other hand, is a true high resolution touchscreen, and so far with about half a month use it seems just fine. Fingerprints wipe off both easily. Speaking of which, I'll have to post a tip on how to quickly clean the pronto without sending out all sorts of signals or switching modes... :-)