Me either, but I take great care to put them away dry and oiled/greased. Rifles are not covered.all my handguns are in soft pistol cases in my safes. Never had a problem.
Now, using the smaller rare-earth magnets to hold mag pouches would help isolate the mags from the magnets. (And would help where a person had no-ferrous, or polymer mags.)although the repeated rubbing may eventually magnetize the mags, which would mean they'd be prone to pick up ferrous particulates from soil, which could mean otherwise unwarranted failures