Quote from pilpens:
"I have been reading more about this and slowly seeing that keeping mags loaded may not be as big an issue as I thought it was.
1. As long as the constant load on the spring does not stretch or compress the spring over its elastic limit, then springs should be OK.
2. Repeated cycling can weaken spring similar to what happens with recoil springs.
I am starting to see that the cycling is more of an issue that keeping mags loaded."
+1
That's my understanding too.
However, just for fun, I shoot up my carry ammo and then load a fresh magazine about every 3 months.