Another main thing that kills the battery's is using the laptop with it plugged in all the time and not actually using the battery by itself. This will KILL the battery faster, its best to fully charge it then fully drain it to keep it at peek performance. If you are like me and like the performance better when plugged in TAKE THE BATTERY OUT, just don't pull the plug
Doing it this way a battery can easily last up to 3/4 years and still hold a charge as good as day one.