This is the outdoor track I run at and was getting 15 minutes with the 1512 2.5d and 4s 5000. It is one of the larger tracks in the country.
www.leisurehoursraceway.com
It wouldn't surprise me if the 2.5d and a 5000 pack dumped a little before 15 minutes in certain conditions at other large tracks depending on battery quality and LVC. I never had a problem with it though.
I have consistently burned 210/mah with the 5s and 1512 3d (1700kv). I changed over to the 2.5d (2050kv) and ran it on 5s geared appropriately around 40mph and my efficiency dropped a bit as I burned 271/mah per minute due to the increased RPMS. 31,000 vs 37,000. Just some food for thought.