I second Shakey's point; when the transmitter turns off it stops broadcasting a signal. It's up to the receiver to decide what to do when the connection is lost. I'd personally happily run a Lemon on a Heavy. You can set their failsafe to what you want when you bind them, and they do exactly what you need from an RX. I've never had one die or lose signal apart from when I've gone and broken one with my dodgy soldering. The chances of your receiver dying or fail safing incorrectly is far below the chances of a wire coming loose or a connector coming undone, often with similar results. So as long as it does control your robot and does fail safe, I wouldn't lose too much sleep over what Rx you're using...