Battery Life on Macbook Pro

It's likely that you are running something in the background (such as Skype) which is triggering your dedicated graphics card, despite it not actually doing anything graphically intensive. This is a known issue in Apple's graphics card switching technology.

Download and run gfxCardStatus and see if I'm right. If so, close the problematic program or use gfxCardStatus to manually switch to the much lower-powered integrated chip. You should get longer battery life after that; I haven't directly measured it but I know I get at least 30 minutes to an hour of extra life.

And of course it also depends on what you're doing with your computer, what background programs are running, the brightness of your screen, etc.

I have the same Air as you and I am getting 5-6 hours. So not to much off of what the advertised amount is. Your battery sounds faulty to me.

The last computer I had had a faulty battery. It was replaced for free and within a couple of days. Back then they simply replaced the battery on the MB because it was removable. Chances are now they will give you a new laptop because the battery on the Air is harder to remove. You might be without a computer for a few days though. I don't know what they do in other countries, but in Spain they just took it and mailed it to Holland to get fixed and then mailed it back.