Acer Aspire s7

I've been reading reviews and was wondering is anyone had experience with the machines. I was looking at the 13.3 inch with an Intel i5 ivy bridge. 2 questions.

How's the battery life?

What do you think if I wanted to keep this device for 4 or 5 years because it only comes and cannot be upgraded above 4 gb of ram? I've read that only 4 isn't exactly future proof.