I use the car dock to and from work where I use it to listen to music or check traffic.
At work, I tether when I am at my desk. So, it gets a charge during the day.
At home I use my desktop on the weekends, or if it drops too low before going to bed.
I used to plug it into the wall at night, but the battery is virtually unchanged from when I go to bed and wake up now.
Now that I have had it for a couple of weeks, the battery life is better than my Storm was. If anything, I charge it more than necessary due to tethering.