I won't store a mag loaded for long term and for the firearms that I do keep ready, I alternate mags occasionally. I have had issues from mag springs weakening over time with storage.
Has anyone else never noticed that when you first buy a mag, some of them can be a real pain to load to capacity (especially some pistol mags), and after a while, they're easier to load?
Or perhaps you have a gun stored and buy a new mag. When you load them side by side, can you not tell a difference in that the new one is generally harder to load?
I also admit that I never store a firearm with the hammer cocked for the same reason, although that is also among other reasons.