[pgdion]

Didn't see any mag springs compared to valve springs. I see lots of claims that the springs where out from compression / decompression. This failure mode for a spring, called fatigue, is not likely to occur in a magazine spring with it's very slow rate of compression and decompression and, even under heavy use, a very small number of cycles compared to what a spring is designed for. I would guess the shock from firing is harder on the spring than the cycling itself is. The valve spring was mentioned as an example of where spring fatigue is of great concern, where a spring may be fully cycled over 50 times a second and a cycle may take a few milli-seconds. It's used as a differentiator, not a comparison ... an example of why I don't think spring fatigue from cycling should greatly affect a magazine spring. What I have seen first hand with most magazines is how hard it is to get that last round in when they're new. They loosen up over time and I believe it is from the heavy spring compression each time you push in the last couple of rounds, each time it relaxes the spring a little more. I believe if you want your springs to last the longest, don't load the last couple of rounds and leave them there.