Just out of curiosity what phone did you have before the GNex?
I bought this phone and the 2100mah extended battery but didn't activate, used it on my wifi connection for a week before I decided I wanted to use it as my main phone. I heard how bad the battery life was so I downloaded the two apps I have to have on my phone. Facebook and The Weather Channel, I setup my Gmail account and that was it. I charged the phone over night, got up at 7am for work, took the phone off the charger but didn't touch it. I let it sit from 7am till I got home around 5:15. The battery was at 70% when I got home. The screen was never turned on, it wasn't connected to the VZW network. It was just using WiFi and updating facebook and my gmail and I lost 30% battery life. The phone I was using at the time was a iphone 4 and I was still at 80% battery life on that and I used it a few times during the day. Go figure.
I've come to the conclusion that you can either worry about your battery life or just use the phone and charge it when you can. I've had a few Android phones and have always had crappy battery life with them. Its just how android is. I love the phone and Android but the OS is horrible when it comes to battery management.
People have suggested turing off 4G, don't let facebook sync or any other of your app sync, turn down your brightness and a few other tips and tricks that will save some battery but my whats the point of having a phone that can run 4G and do all this stuff if you can't use it?
My suggestion, buy a car charger and bring your charging cord to work with you and charge this thing whenever you get the chance. Otherwise your going to be pulling your hair out trying to figure out the secret to saving battery life.