Then

“It’s almost impossible to believe, but during our initial tests, using the iPad pretty heavily, downloading and using lots of new apps, doing some 3D gaming, watching HD video, all the while getting email downloaded in the background, we got just about what Apple claims this device will do. In fact, it went a little better — we managed to get 10 hours and 43 minutes of life out of the iPad before we had to plug it in again in our first run through. That’s pretty crazy endurance considering what we were doing with it.” – Engadget’s iPad review, 3 April 2010

Now

“The bad news is that some compromises were made — specifically in the area of battery size … the [iPad] Air 2 squeezed out 11 hours and 15 minutes…” – Engadget’s iPad Air 2 review, 21 October 2014