I just came across this video on Youtube from DJI where they demonstrate their claim of a 25 minute flight time for the Phantom 2 vision with a demo flight:
So far I have not been able to get my IRIS close to the 15 minutes that 3DR advertises. Even without any camera or front mount. Only way to do so is to really badly damage the battery.
It would be interesting if 3DR could produce a similar demo video to the one above and show us how to get to the 15 minutes. Just like with DJI, the flight should be over with the battery failsafe kicking in.