Sorry, meant to add more but got interrupted, power went out, lost the internet, etc., etc.
Anyway, I bought parts for specific reasons (CGW barrel bushings, reduced power firing pin block springs, etc., etc. That kind of stuff. But, to help on shipping I'd also buy a few "spare" parts. Whether ordering from CGW or CZ Custom, might as well add a few small parts along with the parts I need for a specific job/upgrade.
So, the extra small parts I ordered were stuff that I hear of others replacing. Springs (large and small). Pins (that don't really wear out but you sometimes lose.) Slide stops.
When I did an upgrade I saved the factory parts for spares. Sears, hammers, sights, barrel bushings, firing pin block springs, hammer springs, hammer spring cups (I always put the lanyard loop plugs in my CZs), recoil springs/guides, grips, anything that was in/on a new pistol and I replaced is still a good spare for an emergency.
When I replace a factory part with an aftermarket part I put the factory part in the bag the aftermarket part came in and use a sharpie to right on the bag/label that it's a new factory "part" with very little use on it.