[Voodoo Chile]

Power jacks are switched. Whenever a power plug is plugged in the battery is switched out of the circuit. So even if you have effects on a pedal board where all the pedals are permanently patched together with patch cords, as long as the power jack is plugged in to it will not drain the battery.
I leave batteries in all my pedals and never had a problem with leakage. Modern alkaline batteries have a shelf life of several years.
Bill

What Bill said.