I'm not cheap, just thrifty. Why change plugs when the NGK plugs just keep working. They are not going to all stop working at once. I have never had a NGK go bad yet but have been on a tour where a friend with a 47 Ford had ignition problems. We just happened to stop in a lot across the street from a Napa store. He walked over and bought a new set of NGK plugs, installed them and problem solved. If you ever get your car running stick the old NGK plugs you say you bought back in and enjoy the ride. G.M.