Was told, many moons ago, that unless you know exactly why an engine has failed you should not continue with it wind milling for any appreciable length of time, as you can do a whole lot more damage, including write-off, especially since you cannot guarantee lubrication etc. In days of old, when the B707 or the DC8 did three engine ferries the shut down engine would be inhibited from rotating. When an aircraft carries a ferry pod the aerodynamic nose section has a dual purpose, to reduce drag and prevent the core from rotating. Be interesting to know if the engine telemetry still works on a shut down engine and if there is any indication of oil pressure etc. on the flightdeck.