I talked to a buddy of mine about this before. He's in the military and he says he has been handed magazines that have been stored for decades fully loaded and has run them through with zero problems. Like Majorlk said, its the actual flexing in the spring as it is being loaded and as it is being emptied that will wear the springs out, not staying in one constant position for any period of time. I personally have two magazines that I leave loaded at all times for my HD weapon, and all other magazines remain unloaded unless I am at the range. I'm not too worried because I don't shoot "enough" to really be concerned about the springs wearing out anytime soon, I have a set of magazines that are dedicated to being used for HD so they won't wear out, and magazines are cheap enough to replace or replace the springs when they do wear out.