I get close to 10 hours depending on where I'm using it. I keep the auto brightness on and when I'm outside the brightness goes to full which drains battery faster. But with the anti-glare and true tone, the display is awesome. When used mostly indoors for surfing, email, movies, etc with brightness at 50%, I easily get 12+ hours.
Looking forward to the next iPad Pro getting anti glare and true tone. my 12.9 is pretty much useless outdoors and the battery is only about 4 to 4 1/2 hours under that usage scenario. More like 8 to 10 hours though indoors