In general, modern handgun magazine springs will last for years before having any issues. I’ve been told that storing magazines full will have at most a minimal effect on how long the spring lasts, apparently the number of compression cycles has a much greater impact on service life.

There are knowledgeable people who “download” their MSR magazines by a round or two to make reloading easier while the bolt is closed. The practice of not fully loading a pistol magazine is much less common, in my experience.