S7 here. I wear my Watch during the day and then take it off before bed. Yesterday night, when I take it off, battery was around 50%. This morning when I wear it, battery is around 30%. What is the Watch doing throughout the night which will drain 20% battery? There are no heart beat sensor nor activity tracking. If only Apple will make the Watch 'sleep' or 'standby' when we take it off. That would have preserve the battery for the next day.