Does the 2011 13" MacBook Air have a longer battery life than the old one?
Apple hasn't changed the claims about battery life. 7 hours for the 13,3", 5 for the 11,6". It's a bit strange that according to Apple the batter life didn't change. Maybe we'll get a nice surprise.

Found it here: http://www.macrumors.com/2010/10/20/apple-announces-new-13-3-inch-and-11-6-inch-macbook-air-models-with-flash-storage/