I've only had my Apple Watch (42mm S2) for 6 days now. I was finally able to use the GPS on a mountain bike ride on Saturday. We were on the trail for about an hour and a half, but only about 56 minutes of that time was the actual "workout." I paused the activity twice during the ride, at times when we were taking a breather.
I started the ride out at 87% battery, and by the time I had returned to the car and ended the workout it was down to 77%. HR was monitoring my pulse the whole ride as well. I was significantly surprised to only see a 10% drop in battery over that hour and a half. Results may be different from running with a set of different variables. I'm anxious to see how it preforms while snowshoeing. Hopefully we'll get some of the white stuff soon.