Picked the GPS (no LTE) one up on Friday, did a full charge around 10pm. I left it on my wrist overnight and checked in the morning to see if it tracked my average heart rate, the battery was down to 98%. I did my 15min exercise and did my usual Saturday errands. I did my second exercise, at the end of that day I was down at 50%. Today (10pm), it's now at 10%.
I say this can last me for two days without charge.