Does carrying ammo in a mag for an extended time hurt the mag in anyway?

My question is regarding keeping ammo in the mag for a long period of time. My only concern is the spring inside the mag that helps feed the ammo into the gun would get cramped down causing decreased elasticity. Physics tells us that in an ideal system, the spring will always return back to equilibrium, but Does the spring ever loose its elasticity and not feed the gun in real life application? I'm asking because this could be catastrophic in a self defense situation.To counteract this (if it happens) do you change out the ammo in your carry guns and let the spring rest, or once loaded do you keep it in the mag until used? If you change it out, how often?If my question doesn't make sense I can rephrase it!Thanks in advance. via /r/CCW http://ift.tt/2kbgHrq