I am offering advice for stability. I do this every night, before I go to sleep. Unless you need to preserve the "state" of an app, do the following before you go to sleep, or when you are finished with the ipad for the day:
1 - Shut off 3G and Wifi
2 - Close all apps by double tapping on the home screen to bring up the system tray on the bottom of the screen. Hold any app icon firmly to bring up the "-" signs on the icons, and kill all apps from memory by tapping on all "-" signs.
You will have fewer stability issues the next day, and may may have better battery life as well.