My Wilson with a 5" barrel uses a 17 # recoil spring and shock buffs. So far I have 700 rounds through it and the shock buff is still in very good shape. If the shock buff does not last at least 500 rounds you probably either have some sharp edges inside or you need a heavier recoil spring. There are some that don't like shock buffs because if they start coming apart they can cause a malfunction.
That's reason enough for me!