Well with the 9400M, it was more or less about the half (probably lower than half) of what you get in OS X.
if you own a MBP 13" 2011 can you please post your windows 7 battery life?
reason being is that it only has intel gfx so it should theoretically be similar to osx
Probably right around half the OS X time, windows has very poor power management and isn't hardware specific. It will never match OS X in that regard, and it doesn't have much to do with the graphics card.
how does asus produce 10 and 12 hour laptops then? do they run on magic?