I think this has been asked before. Pretty sure it only draws power if something is plugged into it drawing power. So, I just unplug my GPS/battery at night so the light gets full power and charge Garmin/battery during the day.
Rear light is powered through the front light, so if the front light has a switch (all B&M ones do) then that will shut off the rear at the same time (remember the standlight will need to discharge). You only need a switch (maybe a toggle) to control the light/igaro combo.
it doesent, runs all the time, not a bad thing