I saw @LangdonTactical's comments in this post and decided to start a new thread rather than further derailing that one.
Given that you have a pistol you want to use as a long-term carry gun, what parts would most benefit from NP3 or a similar coating? And the flip side of that is on what parts does it have no meaningful benefit? I understand that this will vary depending on the particular gun. And on those parts that are worth doing, should it be done on a new part or one that's broken in? I'm specifically interested in PX4s, but I'm sure the hive mind has suggestions for other pistols that would be worthwhile.