i no use 3s with this set up. 4s mostly and sometimes 5s. i get about 12 min out of a 4s 4000, with a go pro, board cam, eagle tree with osd, guardian, gps, baro alt, and such on board, and a 400 mw 5.8 tx.
if all you carry is a board type camera and one of the mini tx, you could probably get...