[iraiam]

It has been my experience that a properly used magazine will function just fine when it is sored full, even for years at a time, that being said; the several mags I keep loaded all the time get swapped out once a year or so, If I don't shoot that ammo up first.

By properly used I mean if you have a 30 round magazine only put 30 rounds in it, it may hold 31 or 32, but putting more than 30 in it compresses the spring too far and will damage the coils.

I have several milsurp 30 round mags dated 1989 that were stored full for a couple years at a time a few different times, they still function perfectly. Although it should be noted that the springs and followers were upgraded recently, but not because there was a problem with them, I wanted no tilt followers and they came with new springs. I still have the old ones.