Recoil Spring Aging

Have found it necessary to occasionally replace used recoil springs to achieve proper operation. Do recoil springs gain or lose power as they are cycled? Do they get softer due to constant pre-load, or does the wire work harden and get stiffer?

https://www.gunsprings.com/index.php?page=FAQ

Bubba Blaster wrote:https://www.gunsprings.com/index.php?page=FAQ

Doesn't answer my question.

Recoil Springs can weaken they don't get stronger with use and from being under constant stress but it takes a lot of use or could be just a bad spring. I use sprinco because they are built of better steel than many other brands and they last  . brownells sells them.
http://www.sprinco.com/springs.html