Southwood Valley, Cedar Ridge, and Pebble Creek carry most of the 1960s-and-70s housing stock we work on, and the pattern holds across the wider area too - a build range running from 1970 out to 2001, centered on 1976. A door from the mid-70s is almost always a single torsion spring on a steel track, often original, sometimes patched with mismatched parts from a prior repair.
Newer pockets built after the mid-80s tend to have extension-spring setups instead, with different failure patterns like frayed safety cables and worn pulleys rather than snapped springs. Of the roughly 1,979 households we see day to day, 814 are owner-occupied houses, and a good share of those are still running original equipment that has never had the spring touched. That is the pattern we plan around, not a one-off.
The climate band here is moderate heat rather than hard freeze-thaw, but steady heat still dries out lubrication and speeds up metal fatigue on hardware that is already decades old, which is why a spring often lets go suddenly instead of weakening slowly.