How long can I leave a Pt111 mag loaded before the spring begins to fatigue?
not in your life time. sorry, couldn't resist. The springs will not fatigue for many years, or shouldn't. They are made to be consistently compressed so I would not worry about it. What fatigues springs and metal in general is working the metal. Now with that said, use my mags on a consistent basis and watch them for wear. I do that with all my pistols and rifles.You should be good to go.