I am starting to wonder about pumping up these pneumatic s, like leaving one pump in them. I had a Crossman 2200 pumper for 7 years, always put it away empty, the rest of the gun fell apart but the seals were still good. Bought a Benjamin 392 last year, left one pump in it and the seals blew out after only 7 months. I immediately made sure my Daisy 901 and my Benjamin pistol were kept empty, they still work great.
I also had a Crossman 1322 about 10 years ago, kept it empty too. Traded it for a spotting scope and it was still going strong.
Crosman and Daisy say in the owner's manual to keep them empty, but I always figured it was lawyer's talk. Looks like it is one of those opinion things, pumped up or empty?