I'm easily getting around 9 hours of light usage (Safari, coding) on my Late 13 13" rMBP and maybe 4-5 hours of editing photos and "getting stuff done". But what surprises me the most is this thing's endurance when I'm doing virtually nothing, sitting in the library, going through some PDFs and generally just staring at the screen - many times I've seen more than 12 hours of this kind of usage and I'm almost sure it could last for as long as 15 hours with wireless off and without any significant CPU activity.