A possible solution is to set your watch to airplane mode when you know that you cannot be near your phone.My watch burns out after 6 hours because my iPhone is not close enough to my iWatch to keep bluetooth active. So, it sends out battery-draining signals. I cant carry my iPhone with me at work but my iWatch yes. so, I often find the Watch battery dead
Edit - I see that I was beaten by one post. sorry for the dupe.