NO, the spring weakens with compression cycles. I have loaded AR and pistol magazines and left them stored that way for up to a few years, slap em - in fire them, and they are still like new.
I would also note that if you overload a magazine, the spring coils can be damaged and shorten its life span considerably, put in only the amount of rounds the mag was designed for. You can't overload many magazines, but there are some that are designed for 15 rounds and you can actually put 16 in, but you get the idea.
NRA Lifetime Member Since 1999
"I ask, sir, what is the militia? It is the whole people except for a few public officials." George Mason