My mid 2012 Macbook air only gets 3 hours of battery life when fully charged and only using the internet. I usually only use Firefox for web surfing and don't have any programs open in the background (I do CMD + TAB and close out programs I'm not using). Does anyone know why this is happening? I should note the laptop gets pretty warm in my lap and sometimes can hear the fan reving up. Can't figure out what program it could be or if my battery is dying. Thanks for the help. PS - I'm running OS X version 10.8.4. I haven't upgraded to OSX Maverick because I haven't been hearing good things about it, and can't imagine that would effect battery life.