No matter how long your laptop battery lasts, it's not long enough. Sometime, you're going to need more juice, and you don't want to be stuck with a dead battery. Taking a long plane trip is a perfect opportunity to get some work done or watch a movie, but if your battery starts to die, electric outlets in many airports are scarce. Even worse is when your only laptop battery won't hold a charge any longer. Buying a laptop battery directly from the manufacturer will cost two to three times as much as it costs to buy an aftermarket battery online, so shop wisely.