On the topic of keeping magazines loaded. I dug out my Grandpa's 1911 a few years back. The magazines had been fully loaded since WWII. 43' headstamps on the brass. I stuck one in the pistol, locked and loaded it, and fired every one of those crusty old bullets without a hitch. I don't worry about keeping magazines loaded anymore.
On a side note, I have heard of fully loaded magazines swelling the sides of polymer or aluminum magazines. Especially on the AK based 12 gauges.