Loaded mags won't harm the spring. It's the normal compression and decompression of the springs that wear them out.
While cleaning out a gear locker at home I found a box containing several "G.I." surplus 1911 magazines that had been fully loaded with 7 rounds each for 4 years. I know this because the box contained a tag with date and reloadijng data "230 gr. LRN & 5.1 grs AA#2, Winchester primers". They all fired without a single malfunctioning magazine.
Nowadays "rotating mags" has more to do with putting fresh ammo in them than the springs "taking a set".
Ammo that's been continually handled, loaded into chambers via slaming slides, and subjected to 200 degree summer temps inside locked cars/trucks should be rotated to ensure reliablility WTSHTF. :thumb: