jonny.....like you ,dont see them very often,mostly in the climb,due to the weight of the aircraft...from the east coast of the states to the west,especially when the jet is blowing 200+kts,I have seen decent steps to lower altitudes combined with as fuel as you can take and reduced payloads to stop refueling stopovers.....mostly winter ops...had a decent step this winter from intial climb to FL360....down to fl280,due to winds....it happens but not often