I've seen polymer rubs on the slides on my two P-09's that needed to wear away before the guns cycled perfectly. The little Kahr PM-9, CM-9, PM-40, CM-40 hand canons definitely need some rounds before they will cycle reliably. It is the surface coating on the slide rails that might be a little rough for a few rounds, not so much the actual tolerance between the base metals on the slide and the frame.
Triggers (sear, hammer hooks) I never leave alone long enough to see what happens to the stock parts, so I can't comment on that long term. The late plastic gun P-09/07 parts seem pretty stable to me out of the box, but the factory 75B sears/hammers apparently smooth out rapidly. The aftermarket CGW ignition parts don't appear to wear and don't "break in", which is why they are in every gun I have where they can be used. The parts don't change over time. You don't even have to clean them...
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Joe