Yes their design limit is to exceed 1,000 full charge cycles. Quoting from Apple on batteries:

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.

I have been bowled over at how well the internal battery chemistry holds up over time. Of course, bad batteries fail prematurely all the time and need to be swapped, but my gut feel is way more of these "go the distance" than all the older removable batteries.

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.