When I used it for IM Lanza it died about 30km into the run, so probably less than 12 hours. I turned off Glonas to save battery life, but I should have turned off the audible/vibration lap alarms because I think that chews up battery life too. I got chatting to another bloke on the run course who was cursing his 735, which had given up at about the same point as mine
I usually use the live track function when I’m out cycling so Ms W can see where I am and doesn’t worry about me and this seems to be very heavy on the battery. I think I usually only get 6-7 hours of battery life on GPS live track.
I’ve generally been pretty happy with mine, but the original strap lasted less than a year and after about 2.5 years the face and internal gubbins parted company with the rest of the case. The watch continued to work and I glued it back together, but I wouldn’t trust the waterproofing for swimming now.