Man! I hope that's not the case. I have had a bunch of mags topped off for a long time. Modern metallurgy has eliminated that problem. Anything made in the last 50 years will handle it. That said, some of the cheaper polymer mags will deform at the top and cause FTF problems.
Only mag springs I've ever seen have issues is on my tube fed shotguns when they've been loaded for a couple years. My wife found loaded ar mags I forgot about and packed away 4 years ago and they shot fine yesterday.