We recently purchased a dual tap kegerator with a 5 lb CO2 tank. We've cashed 5 kegs and the regulator still says there is about 500 psi left in the tank (I keep the tank in the fridge, which I know impacts the psi reading- is this ok?). We haven't experienced any CO2 issues and I'm just wondering when I might expect it to run out. More specifically, how many kegs can I empty before I run out of CO2??? I use the gas to force carbonate and serve.