It's nearly impossible to tell someone how long they'll get, there are so many variables to battery usage.
Display brightness, if you're in a strong 4g area, how much the screen is on, if you stream music/video ect...
I personally get around 12-13 hours a day and I would consider my usage a little below moderate and I use 80% brightness. If I knock the brightness down to 30-40% I can get much more out of it.
^^^
THIS
Another thing to consider - are you going to leave it stock or run a custom rom? Custom kernels can add a few hours to your battery. With that being said, the extended battery gave me an extra 3 hours of use. I get anywhere between 12-18 hours depending on my screen time on and how hard I hammer it during the day. Just to be safe, if I have access to a charger, I always charge it so I don't have to think about it.
EDIT:
The two things that kill the battery on the Nexus
- Screen - if you can lower the brightness this will help tremendously
- LTE - if you can connect to wifi - do it, it will help a lot as well
Probably leave it stock.
So if I manually switch to 3g will that save a lot more battery life?
Hey Wookie, do you leave the extended battery cover on with the standard battery? I can't find my standard battery to see if there is space between the extended cover and standard battery, and if so does that make the back fall off, or feel weird in hand?