iPad Air 1 = 14hrs 45mins usage and 3 days 15hrs standby with heavy use of Safari and playing Trials Frontier and then misc usage of other networking via wifi apps and some other games.
Auto brightness setting enabled and using IOS 8.2
Now this is good battery life. If I was using tablet lightly here and there could get 16+ hours or more usage.
No IOS 9.x for me!