Oh, you sure can wear through metal with rubber, look at an old marble stair case. My old middle school has huge divots where nearly infinite children have trod. The bigger abrasive is the road grime that your break pads trap and then wear on the rims. I've never worn, no have I heard of wearing through a rim by breaking. If you did however, it would be spectacular. See if bontrager wants to sponsor you for riding that much as a witness to their quality. As for gear, sorry, you'll have to get someone elses suggestions. I just don't keep current with that stuff.

i think that there are gauges you can buy, or techniques for measuring the amount of rim that you have left. unfortunately, though, all rims, alloy or carbon, wear out. the only ones that don't are disc only, or track rims.

if you do wear them all the way through you should send pictures. :) I have a degree in Chem E with a focus in materials. I like seeing things break.... enginerds...