What's Your Parts Replacement Regimen?

[alx01]

I have Sprinco springs that have been in place for years and unknown round counts. It's actually one of last things I worry about.

Gas rings are replaced when they fail the gas ring test. Almost all of my extractor springs are Sprinco as well.

Fire Control Springs are replaced based upon appearance during inspection.

Gas tubes are replaced when the top of the tube engaging the key becomes worn down.

What's the criteria for appearance of for fire control springs? Rusted, bent, weak, etc?

Do you have any experience or recommendation with replacing EJECTOR springs with Springco?

[tom12.7]

There's a lot of variables at play here, and a lot of different valid reasons for some different methods. Does it need to run as new for "X" number of rounds after maintenance? Are we looking for a point that items like or similar to spring tension issues are at a point of failure or at a operable set span of function before that? What is the base criteria for the OP? We could look into this in many ways. Nobody wants to replace parts without the necessity to do so, but pretty much everything in this system wears at varying rates depending on particular combinations.
We could look at this with different levels of inspections, with a safety factor. Lower levels require higher parts change intervals. Mostly, this is due to the level of capability of that level. In a general progression from unit operator to armorer to lab with the base criteria of operation required for use. The vast majority simply do not have means required for in depth inspections, nor do they have good experience to do so, they have no need to know that. For the most part, it tends to be safer to replace questionable parts with a good quality replacement, but sometimes the parts that had been replaced may be fine for the intended use.
Even simple parts like gas rings, action springs, extractor springs, etc.. do have vastly different lifespans depending on combinations presented. The gas ring test, while normally good for the most part isn't as conclusive as some other tests or trends. The gas ring test, for this example can very well end up in a result that changes the rings without the necessity to do so, but it is normally in a safer place than what could be without looking at it some other ways for MRBS and MRBF.
There's a lot of things that we can look into if desired, but there's not many simple answers. A lot depends on the OP's requirements for the results.