Most of the housing stock across this service area went up between 1971 and 2003, with the median build year sitting around 1985. That's the window when torsion spring setups became standard on new construction from Charlotte Park out toward Harbour Heights and Burnt Store Marina, and those original springs are now well past their design life almost everywhere you look. A spring rated for a set number of cycles doesn't know or care what year it is, it just wears out, and a lot of the springs on doors built in that 1980s-90s run are the original ones, never swapped, just slowly losing tension every time the door goes up and down.
The mild temperate climate here actually works in your favor compared to places with hard freezes - you don't get the metal fatigue that comes from repeated freeze-thaw cycling. What you do get is steady humidity and salt air working on the coil over decades, which corrodes the wire from the inside of the coil out, not just the surface. A spring can look fine on the outside and still be down to a fraction of its rated strength. That's why a spring that's carried a door fine for years can let go with no warning on an otherwise unremarkable morning - it's not one event that breaks it, it's thirty-plus years of cycles and coastal air catching up at once.