Knock on wood, but I haven't noticed any leak concerns on mine. It's a fun gun though.
Here's a potential idea though. When the pressure in your line meets the pressure in your gun on the way up, you hear that click in the fill port opening. You could fill to 3000 psi. and disconnect. If you grab your gun a week later, hook up to the fill fitting, and you hear that click at 2500, then you would know it has leaked down between sessions.