Just to momentarily go back to the original question (by the way - I have never used speed brakes, reverse thrust or wheel brakes - it all stinks of poor energy management to me!!) - Long ago when I flew the Tucano, some airframes did have a 250kt restriction on the 'air-brake' (as it was called then!) and with a Vne of 300kts it always seemed quite strange that you had to wait to slow down to be able to use speed brake. I believe this was a structural limit on the actuator mechanism which was straining and bending under the hgh loading at faster speeds. In time they were upgraded and I think that they now all have a 300kt limit.