Should you empty your rifle's tank or refill it when you are done shooting?

Best case on paper, is keep it filled to just above the setpoint for the regulator.

Worst case on paper, is to leave it empty, only because you may have trouble seating the exhaust valve when you refill.

In actual practice, it really doesn't make a damn. If it's gonna leak it's gonna leak, and it's usually from orings taking a set and becoming not-so-pliable anymore.

Shoot more and worry less.