1/1000 has been my idea also, for a gun that may be used to anything a bit more serious.
But depending on the gun type, one probably also has to consider the overall round count. Some guns can only take so many rounds before they are ready for the trash bin, or a serious rebuilding is in order. For example, a friend shot circa 20K rounds (+P) through a SigSauer P226, and the frame had been cracked in 3 places. That particular pistol had effecticely become scrap metal.
But depending on the gun type, one probably also has to consider the overall round count. Some guns can only take so many rounds before they are ready for the trash bin, or a serious rebuilding is in order. For example, a friend shot circa 20K rounds (+P) through a SigSauer P226, and the frame had been cracked in 3 places. That particular pistol had effecticely become scrap metal.