Early 1970s versus newer
That six-year gap matters more than it sounds. A door and opener from the early 1970s has had more cycles, more heat, and more of the region's mild-but-not-dry air working on its steel than a door from a house built in the late 80s three towns over. What you can actually do yourself: pull the release handle and check the door balances at waist height without your hand on it.
