long hours of gunnery-practice , until temeraire could hear a full volley of eight rifles go off behind his ears without so much as blinking ; crew maneuvers and drills until he no longer twitched when he was clambered upon or his harness shifted ; and to close every day 's work , another long stretch of endurance training , sending him around and around until he had nearly doubled the amount of time he could spend aloft at his quickest pace .