Cycle count accumulation
A torsion spring rated for roughly 10,000 cycles, installed in 1989, has been through a lot of open-close cycles by now - more if the household uses the garage as the main entry, which is common in this housing stock. Add cold-moderate temperature swings that stiffen lubricant and shrink metal tolerances in winter, and you get the classic failure: a spring that snaps on the coldest morning of the year, not gradually.