I bought a very lightly used bca float throttle 22 avy bag this summer. This is my first avy bag so I'm a little green when it comes to them. The canister came to me empty and I got it filled in November. I'm just preparing for my first mountain trip of the season and I noticed the air pressure is way down. Gauge is reading 1000 psi. What happened and how can I prevent this from happening again?