This is often a result of the battery not reading accurately. You can calibrate it by letting the battery drain down to zero and powering itself off. Then recharge it to 100% and test to see if the battery life has gone back to where it was.
Ok I needed to put it on the charger at 26 hours because I need it for work but still had 36% left. I did wear it the entire time. I had the brightness all the way up, raise to wake on, and 70 seconds on. This update really helped!
My watch has been pretty great up until the last update. Still not awful. But not as great as it was. Not sure why.... Maybe a App Update is not playing well with the watch. I'm also getting old texts and previously viewed notifications back. Which is a little annoying.