The reason why I asked originally was I thought it was bad for the springs in my mag to keep it full.
Could be, over time, but it would have to be more than just thirty or forty years. A friend of mine came into possession of a loaded 7-round mag that had been brought home from what came to be known as WWI. It had been misappropriated from the Army along with a 1911. The 1911, however, didn't make it. As I recollect, my friend got it from the soldier's widow, and, in the sixties, inserted it into a 1911 and fired seven rounds with no problem, except he probably had to clean the gun afterwards, since that old stuff was corrosive.