I'm wondering what are the main failure points of magazines? I have a lot of Gen 3 pmags but I've heard that over time the lips will separate or whatever if you leave them loaded for a long time.

I've also heard that the little dust covers are designed to alleviate pressure from the feed lips so they can be stored with less concern.

I have no idea if that's true or not.

What's a good idea/schedule for storing loaded AR mags for say a night stand rifle? Anything that I should be aware of?