The battery life is very good.
If you want to extend the health of your battery then don't drain it down very often if possible. Lithium ion batteries love being topped off. Remember, there is no memory with L ion batteries. If you are in your car. Plug it in. If you stop at the office or it's convenient plug it in. The less charge cycles you have the longer the battery will last in the device. 1 charge cycle is a complete discharge from full. Also, the "calibration" of the battery only refers to iOS and the battery meter. Something that really does not need to be done but once every few months or so and does nothing for the battery itself. All it does is make your battery meter slightly more accurate.