I'm looking to replace my Win 8.1 tablet which lasts 8hrs max purely for ebooks. Can anyone chime in with battery life from start to death reading via Calibre with brightness around 40%-50%? I'm looking at the 11" 128GB Air, possibly with 8GB RAM to ensure futureproofing (for the OS, not for ebooks). The other choice is the Lenovo X240, which can hit 20hrs, and around $200 more. Anyone (and no I don't want an Ipad) - ?