I dont have a lot of practical experience, but i remember my powerplant
instructor insisting that if we ever dropped a plug, they get replaced,
even if new. Then what happened? A student knocked off a whole spark
plug tray with 6 plugs on the ground. Instructor wasnt very happy about
it. Had to get 6 new plugs for a plane that never leaves the ground.
Just my experience.
Jesse M.