My 2 cents - my battery life is dependent upon what I'm doing. Simply surfing the web, it could go upwards to 7 hours (mostly because I have the "dim display" turned off). Using Lr and PS CC - 4 to 5.
There are specific circumstances you need to do to get that 9 hours - turn off Bluetooth, make sure the "dim display" is turned on, and...no Flash sites.
Keep in mind that even the best WinDoze computers really can't do that good. My wife's latest laptop is supposed to have up to 9 hours. She averages 4-5, and that's just doing email and web. The culprit? You guessed it - Flash.