I had some of the first RevMs loaded to 30 with the covers on in storage for 7 or 8 years.

Most of the covers had popped off but they all worked fine.

I think I have 5 or 6 loaded mags at any given time and about 10 training mags that I use. I don’t really like having loaded mags in storage as ammo is kept in cans in a safe. Mags are mostly in the attic.