In my experience, no. My first pcp, was an fx bobcat mk1, which I bought used some years ago. I store it with whatever pressure is in it. As far as I know the previous owner did never service it, and since it is a mk1 which was unregulated, it should be relative "old". I do not shoot it that much now, as I have other guns also. But I always store it ready to shoot, and that usually means over 160 bar, or full bottle. What I never do, is to store a regulated gun below reg pressure, as I seldom shoot them that low. I do not know if the reg would feel good about staying open, so I always have enough pressure to keep it closed. I like to have my guns ready, as I like to fill after I am done shooting, not before.
