Depends on use and intended purposes. For lightly used with plinking level loads probably never unless I notice battering of the slide. Most of my purposeful guns are usually tuned to some level. Several of my Beretta 96's I've gone +60% on the spring Rate and they will lock back with cheap plinking loads with very gentle recoil while handling +P etc loads without abusing the gun. Similar with my 357sig. A lot is dependent on the user. Most of my tuned guns will limp wrist for most people under 200lbs though.Just out of curiosity, how frequently do you change the recoil springs in your pistols?