The answer is Yes to both question. If you are using Apecs Electronics there is a power drain whenever the units are left on whether asleep or not. To save on the batteries you should turn them both off and just turn them back on prior to diving. I always calibrate the day before diving and then check if I still have proper reading when I turn the units back on prior to diving and if they are too far off then I would recalibrate, but so far it has not happened.
As far as drain on the batteries, I have had a couple of senior moments and left the power on for a couple of days after cleaning the unit and playing with the controllers just to find out that I spent the batteries because even though they units are on the sleep mode they do still drain power.
