On a torsion spring that's original to a 1972 install, we don't just swap the spring and call it done - we check the drums and cable for wear that's been building the same fifty years, because putting a new spring on a worn drum is a callback waiting to happen. Openers get tested under load, not just cycled empty, since a door that's heavier than spec (common on older steel doors here) will trip a modern opener's force settings even when the opener itself is fine. Cold matters too: this area sits in a moderate-cold climate band, and a spring that's tired handles differently at 20 degrees than at 60, so winter calls sometimes reveal a spring that's been marginal all along and just finally gave out. We fix what's broken, not what's merely old - if the track and rollers are sound, we leave them.