The service area sits in a severe cold climate band, and that matters more on a house built in 1964 than on newer construction. Torsion springs on doors that age have usually done their full cycle count already - years of freeze and thaw make the steel more likely to fail in deep cold rather than in July, and a spring that snaps on a below-zero morning is a common call.
Extension springs, if the door still has the old side-mounted kind instead of a torsion bar, wear differently and need different safety cables - missing or rusted-through cables on these older setups are a real hazard we flag every time we see one.
One more complication worth naming honestly: on a door this old, sometimes the repair costs close to what a new insulated door would run once you add up spring, panel, and track work together. When we hit that point at your place, we'll tell you straight rather than keep billing hours on a door that's better off replaced.