No and no.
The conventional wisdom around here is that it is the repeated cycling (compression and decompression) of the spring from use that will eventually wear the spring. Prolonged storage of a full mag should not harm the spring nor affect the function of the magazine or firearm. This makes sense if you think about the shock on a car. They really only eventually wear from use.
I have had full mags (Beretta 92FS) sit for much longer than six months with no ill effects. When brought to the range both magazine and gun perform flawlessly.
Even with use your magazines will last a long time. And if they do begin to wear the fix is as easy as installing new springs.
Hope this helps.