Actually mag springs are under more of a load when the mag is loaded than are coil springs on a car.
The mag spring is nearly completely compressed, while a car spring is not.
So, this lends some credibility to both our assertions. Yours that is is apples to oranges and mine that they are similar.
What I am saying is if you wish to keep your magazines ready to use in the event of emergency do as we did in our LEO department. Have enough to rotate them. We would have weapons that actually failed to feed past the third or fourth round because the post they were in had them loaded all the tie and procedure of unloading them to count the rounds every beginning of shift was not followed.
So, if you regularly rotate mags or unload the tension on the spring, you will assure that the failure will never happen. Easy and cheap insurance if you ask me. I am not quoting some statistic I read somewhere, I am telling you what I witnessed in real life.
Mel