How long does the battery last on mid-2011 MacBook Airs?
Battery Life
Apple's documentation states that the battery of the Macbook Air performs just like the batteries of the Macbook Pro:

The built-in battery of your MacBook, MacBook Pro or MacBook Air is
designed to deliver up to 1000 full charge and discharge cycles before
it reaches 80 percent of its original capacity.

In addition, Adaptive
Charging reduces the wear and tear on the battery giving it a lifespan
of up to 5 years.

During this lifespan the batteries will have a fast charge to 80% of the current battery capacity (2-3 hours). [source]



Battery Maintenance

Do not leave your Macbook plugged in all the time. The battery juices need to move from time to time. It's recommended that you charge and discharge the battery at least once per month.

Temperature: Keeping your Mac at room temperature (22°C/72°F) is ideal.


Long Term Storage: Apple recommends that you store the battery with a 50% charge, if you are not planning on using it for at least half a year.


The innovation in the design of the battery of the Macbook Air was not about increasing capacity, but about the ability to manufactures them very thin. The batteries of the Macbook Air are located towards the thin end of the Macbook Air.