Earlier quoted context omitted.
How long does your battery last under Linux, with reasonable screen brightness? What's the battery discharge rate indicated by powertop? Are you using a full desktop environment?
I run a very minimalistic environment without a DE. I use XMonad as a WM. My only graphical applications are Firefox and Zathura. With wireless on, while browsing the web, powertop shows around 5.2W. This is with a pretty bright screen. With reasonable usage, you can go well past 5 hours. Note this machine has a tiny battery in comparison to the 13 inch model. I believe things could be even better (-0.5W) if I used a…
EDIT: I should add that I've only spent time in 10.9 on this MBA 11 2013 model. I've been told the battery life in 10.9 really is quite a lot better than in 10.8.