I have a Gov. Model that was converted to Bullseye specs before I got it 20+ years ago. How often do I need to replace the spring? Current one is what came in the gun. I use this one for about 400+ rounds of mid-range loads a month. The only wear I notice is on the bottom lug which is flaring slightly from contact with the slide stop pin. Gun has at least 15,000 rounds through it since I got it. Brass is normally about 3-6 feet right rear.