Spring test/replacing

Who here measures their recoil and main springs?

I pulled out a Wolf 12lb spring and noticed that the spring length is drastically shorter than a 14lb spring that I replaced it with.  I seen a few "spring checkers" for sale and simple plans to make one.  So do y'all replace them after every season, go by round count, or just check them periodically?

I check them before I put them in, and periodically for the ones I am using. A spring gauge makes a drawer of unlabeled recoil springs much more useful.

Spring testers don't have to cost a million bucks.