Given that the 9mm models were designed for +P and are all steel, I wouldn't worry about wearing them out. It may not be such a bad idea to replace the recoil spring assembly after 10,000 or 20,000 rounds. Kahr didn't take any shortcuts in design or materials with that weapon. .40 worries me, in general, but the K40 should last as well as most other .40s do.