Made me look up mine. Still every 10 mins for most of the day apart from workouts. Once a 20minute gap, and once an almost 3 hour gap!
I was pretty much at my desk for most of that 3 hrs, I wonder if it was a bug, or maybe if the motion sensor detects low movement it slows down the sampling rate.
I'm going with bug.
perhaps you are correct. i'll give it longer and re-evaluate.