So, I think I've found why some are experiencing battery drain.
I have an IQConnect field which provides vibration alerts if I fall outside of desired zones (be it pace, hr or power) - and after finishing my run on Sunday, I noticed my watch was still buzzing, even thou I had completed the run, saved it and was back to the normal watch face.
I had it a few days previous and thought it was just the move goal thing - and back then noticed the battery drop.
Pressing the workout / activity button to start a new workout (and not doing anything else) seemed to stop the buzzing
Just wonder if this is a bug - and one which is causing the massive battery drain on some.