I'm considering buying the fully loaded macbook air 1.8 i7 with 4GB Ram and 256GB SSD. I currently own a white unibody macbook 2.26 core 2 duo from 2009, with 8GB ram and an SSD, and with a reasonable 5 to 7 hour battery life, but I find that carrying it around all the time is killing my back. Is this a good upgrade? Even 3 years later the macbook air still offers only 7 hours. How appreciable would the increase be to an i7 from a core 2 duo 2.26 and the air's faster internals? Should I wait for ivy bridge and USB 3 and maybe a faster processor and longer battery? Is the 4GB ram on the air enough for computing in the next couple of years? I really want to buy a new computer that will last me at least 4 to 6 years. I definitely don't need to upgrade at this instant, but I really want to.