Housing across this part of the metro went up mostly between 1957 and 2005, with the typical build year sitting around 1977, and most of what's still standing is 1960s and 70s stock. That era used torsion springs and galvanized lift cable that were solid for their time but were never built to run forty or fifty winters. Add a cold-climate band with real sub-zero stretches, and you get steel fatigue that shows up as a sudden snap rather than a slow wear-down. Cold also stiffens the lubricant in rollers and hinges, so a door that worked fine in October binds and strains in January, which speeds up spring failure and cracks plastic idler wheels. A lot of the openers from that build period are also original, and their gears wear out right around the same time the springs do, so one failure often surfaces the other.
We can't carry parts for every obsolete opener board from that period on the truck, and some of those drive gears take a day or two to source. That's the honest limit: on a 1970s door with an orphaned opener, the spring gets fixed same visit, but the opener sometimes waits on a part.