I should start off by saying that I'm an Apple Watch newbie. My first AW is the SS Series 3, picked up on Monday, October 2. My carrier (Telus) has not yet offered LTE, so I'm using the watch with my iPhone. I turned off the power-saving option for Workouts, activated Bluetooth for music listening, and use the phone from about 6:30 AM to 10:00 PM each day. And, I use the workout app a lot. The battery life under these conditions has been more than acceptable, usually at the end of the day, I've still got an indicated 50% battery life.
I will get the LTE activated as soon as the carrier offers it, and if I notice a significant change, will certainly report out.