Not something I would normally do but I had flat batteries whilst at anchor last week. I only had the radio and fridge on but I think my son left the tv inverter switch on and thought that may have contributed.
I think they were all past their sell by date and so now replacing all 5 batteries for piece of mind.
Mine does - I was checking the manual for it only the other day and happened to notice this.
Mine is a Victron Atlas Combi 800 and it has "on", "off" and "auto" positions - "auto" consumes less power than "on" when not in use, but is apparently unsuitable for some types of load. Both "on" and "auto" consume some power even with nothing plugged in.