Fly with DX7 (or any other 2.4 GHz system) for several flights, then fly 72 MHz. There is a fairly good chance you will forget to pull up the antenna. I've done it, and I know several others that have done it. Usually, only once, though. If you don't think so, well, wait. It will. You may be fortunate enough to catch it before any damage is done, but often, you are to much in trouble and trying to do something to save the plane to realize that it's down until after you pick up the pieces. Ouch is right!!!