Howdy
I have found no good answer for that problem. And no brand seems consistent. I had a issue 45 mag that came with a gun that I bought that had been loaded for 12yrs(?!?)and it worked and still works fine to this day. 7 round mags don't compress the spring as much as 8s do. ISMI seems to make as good or better than most. What I have been doing for years is rotating my carry mags on a 3-4 day basis so one doesn't stay packed for a long time.
Hope this helps!
L8r
Conley