It depends what you're shooting, too. You wouldn't dream of shooting 500 rounds of .357 at one session would you? But that many rounds of 9mm wouldn't be so bad, cost not withstanding.
It used to be recommended that you keep up your practice with a similiar model handgun in .22 but I don't think anyone actually does that anymore.
Shoot low, sheriff. They're riding Shetlands!
Underneath the starry flag, civilize 'em with a Krag,
and return us to our own beloved homes!
Buy War Bonds.