In another requirement to ensure its survival, the model cycle of Lincoln was extended from three years to nine years. While largely dispensing with major yearly model changes, the decision established design consistency and shifting resources towards quality control. For 1966, to better compete with the Cadillac Coupe de Ville and the Imperial Crown/LeBaron Coupe, Lincoln added a two-door hardtop to the Continental model line. After the 1967 model year, Lincoln ended production of the Continental 4-door convertible. At 5,712 pounds, the 1967 Lincoln Continental Convertible is the heaviest non-limousine car ever produced by Ford Motor Company; as of 2018, it is the final factory-produced four-door convertible sold in North America.