No such thing as a "high speed turnoff" I think you mean"rapid exit turnoff". Therein lies the problem, rapid exit allows you a 45 degree (or less) turnoff instead of 90 hence the rapid exit, the "high speed turnoff" brigade frighten the s**t out of me especially the BA shuttle to LGW who seem to have abandoned the use of reverse thrust and depart the runway still under heavy braking. 25 to 30 kts with the speed under control is the only way to leave using the RET.