even with switchable graphics?
That would increase battery life but even with on-board graphics, to get 5 hour battery live you will want a netbook if you will use the PC for those 5 hours. Screen is a huge drain on the battery, the bigger the screen, the more the drain. And the i5 is not the best platform for low power use. An i3 with on-board graphics with the screen not at full brightness may be able to get you more than 3 hours though.