In a recent test I create a timer induced function. I enabled the face and placed the watch down on the desk. I expected it to time out after a while, that the timer called function would stop running. I expected it would stop running in a minute or less of inactivity. After a few minutes, guessing 4, I decided it was going to keep running. Is this a bug in the firmware, or did I simply not wait long enough, my understanding being that the watchface will exit low power mode when it detects the user has lifted the face to view, but then return to low power mode after a set time. Or maybe the detection is based on the watch face pointing up?
It is my understanding (from this post) that the 920XT 2.64 firmware doesn't support the high/low power mode functionality and it is just for testing your watch face works correctly in the simulator at this time.