If you ever have a real need for more than a couple of magazines, your problem is not a shortage of magazines. It's a shortage of people on your side of the argument.
Agreed however my 60 are for a few reasons. I work in the industry and run my AR's a lot. I too believe they are a general replacement part that go bad. Generally speaking 90% of issues you run into an AR is caused by bad magazines. Pmags simply hold up better than the metal GI mags in my experience, however they too, don't last a lifetime with the amount I shoot.
Also I try to keep at least 6 mags for each one of my AR's.