At 100% brightness, how long your ipad 4 battery can last? Mine is now 24% after running 5 hours. I highly doubt I can reach the legendary 9 hours plus.
I seriously do not know a single person who uses his iPad, or even iPhone, with 100% brightness - except for when they use them in really bright surroundings.
Heck, in normal conditions my brightness is often (well) below 50% - which I consider bright enough. And Apple does its battery testing at 50% brightness.
Apparently, you're still able to get a total of 6.5 hours of battery life at 100% brightness at this rate. I think that's just fine when the brightness is set that high.
Best tip: use your iPad with a lower screen brightness. Best way to adapt? Use your iPad at, for example, 30% brightness for a while and after you have adapted a bit set it at 50%. Than you'll see that 50% is actually very bright already (and that's because after a while you get used to that 30%).