i was taught that you only raised your flaps after clearing the runway, keeps the runway in working order...JUST in case....you pull the wrong handle...and raise the gear !!! it used to happen quite a bit, now they have interlocks and micro switches to prevent this happening. also, leaving the flaps down during the rollout causes lots of drag and slows the aircraft. the spoilers keep it from flying no matter how fast its going (within reason).