I have noticed this since I bought the watch. A few weeks ago after a long run, the battery life seemed to drain really fast for a watch with a reported battery life of 20 hours. So what I have been doing is fully charging the battery on the watch and record my activities then turn it right off so it is on ONLY when in use. I did this for a few rounds and notice it last only for 8-9 hours total! I was able to replicate this few times. I realize using a power meter, HR, foot pod, etc would probably decrease the total time so it is not 20 hours...but 8-9 hours? I owned a 310XT prior to the 910 and definitely put it through its paces with the same Ant+ stuff and the battery life was amazing, so to see this issue with the 910 is disappointing.