I used to own a 229 in .357 Sig. I sold it because I could'nt afford to shoot it. Factory ammo is very expensive and reloading is problematic with a bottle necked cartridge. It is also VERY noisy. When you shoot on the line, you have everyone's attention.
My guess is that your eardrums, wrists, elbows and pocket book would wear out long before the Sig did. If you could afford to shoot XX,XXX thousand rounds through one, you are rich enough to buy two or three new pistols if they wear out.
BTW, can anyone document a worn out Sig? I have personally seen shot out 1911's and worn out Smith Revolvers, but I have never heard of a worn out Sig.
Best of both worlds? Get a 229 in .357 and a conversion barrel for 9mm. Enjoy shooting the 9mm and be confident that you have a serious man stopper in the .357 Sig when you carry it.
Jay