I have a 12" PowerBook and an external monitor. Usually, I just use the PowerBook in closed lid mode with the monitor. I would like to use the PowerBook's built in screen to have extended desktop, but I'm worried about burning out the backlight if I use it too much. I've seen older laptops, and the displays are usually so dim because of a worn out backlight. Now, I only plan on keeping this PowerBook another two years at maximum, so should I be worried? Am I just being silly?