My Macbook Air 2010 (11 inch) goes black and needs to be restarted every 8 - 12 or so hours
This sounds like a problem with your logic board.

You can run a preliminary hardware test by plugging in your Mac OS X flash drive, and holding down the 'D' key when starting up. See this Apple support article for more info.

A bad logic board usually needs replacing, which can be expensive. Luckily, your computer is new enough that it should still be covered by your warranty.

I recommend that you take a trip to the Apple store so that they can fix/replace the computer for you.