I have been using a 747 as a practice tool for RF Bullseye this winter and have developed a real appreciation for this air gun. I had to rebuild the pneumatics just recently and wondered if the air valve would last longer if it was in contact with the seat of if it would be better left in the "fired" (valve open) condition while at rest? The previous rebuild went about 3000 rounds & began to lose air. The failed air valve showed just the slightest ring in the delrin but I guess it was enough. With parts so scarce, any tips to extend time between rebuilds would be appreciated. This is an addictive accurate little gun to shoot.