OK, Massive difference between Ego, E2 and E1.
E1 does use juice when switched off and a lot of power during firing.
E2 Uses virtually NO juice when turned off, around 0.1 Volts per 6 Months. It also gets around 35-50% (depends on gun) more shots than E1 during firing.
Ego Uses virtually NO juice when turned off, around 0.1 Volts per 6 Months.
On top of that, where the E1 and E2 fire a large mechanical solenoid, and a solenoid valve, the Ego only fires a solenoid valve. It is the mechanical (linear) solenoid that uses the most juice. Also on E1/E2 the solenoid valve is enegised for anywhere from 30-1000 milliseconds per shot, and in the Ego the solenoid is fired for no more than the valve dwell setting, which is normally around 7 milliseconds.
Result! Hundreds of thousands of shots from the Ego per 9 volt. And I recon that if you turned off the eyes (they use more power thatn all the other electronic components, including the backlite) you would be looking at well over half-a-million shots.