I just inquired Kahr yesterday about shooting +P in my P9 Covert and he indicated that they do not recommend a "steady diet" of that as the recoil spring would have to replaced after about 1500 rounds as opposed to 2500 rounds. Extra recoil springs are $7 a piece.
Other than that, with proper maintenance, I can't see why it wouldn't last well beyond 20000 rounds ... especially SS.
Later.