I sure am glad to hear I'm not the only one foolish enough to try this test. Nice to know many others were thinking the same thing back before we had these internet forums.
Or at least it's nice to know I'm not the only one out there wondering these same things.
It's not wearing them out any faster than just shooting them. The Glock 19's mag at work gets loaded and reloaded probably 30 times a week, or more. Longevity on the mag is at least a year. Work that out and you get 1560 cycles in a year, or 260 years worth of cycling mags once a month.
The AR15 would break feedlips on every magazine we put in it until we put a PMAG in it. That PMAG is ugly as hell, and has more wear and tear than 99% of them ever made, but it is still ticking.
Mags rarely ever wear out. Worse case, you wear out a $10 spring and a $3 follower.