Be careful though --- only in "Intelligent Mode" will the motors not shut off with the "Throttle Down > 3 Seconds" maneuver during a flight. They WILL shut off with this maneuver in "Immediate Mode" during a flight.
Also, I asked about this throttle shutoff technique at the official DJI Forums and a DJI tech confirmed that motors will shut off with the left stick maneuver if Phantom is descending in an updraft and it detects very little vertical movement. I realize this situation is rare but it COULD happen --- such as flying in the desert on a really hot day when there are updrafts because of rising heat vortices.
I can imagine in the future, drones will be a lot smarter and use some kind of radar or LIDAR to detect it's proximity to the ground before it cuts off the motors.