[WayneDB]

That's 3.75 hours with a video continuously looping.

I get 6 - 7 hours on a low brightness with normal usage (web, email, visual studio, sql server, etc.)

[Samuel_Michon]

When they performed the same test on a 13" MacBook Air, it held on for 6.5 hours. That jibes with Apple’s stated battery life of ‘Up to 7 hours wireless web’. Apple states the MBA 11" has battery life of ‘Up to 5 hours wireless web’, so it’s definitely more than 3.75 hours.

http://www.engadget.com/2012/06/18/macbook-air-review/