From my reading, the duration of compression doesn't have much or anything to do with it. Repetition of compression/decompression cycles is the culprit in making magazine (and recoil and main) springs fail.
http://findarticles.com/p/articles/m...7/ai_99130369/
However, the basic question of magazine failures is a sound one - and one that I don't think any game system addresses. Ammo, yes. Magazines and similar ancillary items that aren't really consumable, no.
- C.