The mild climate here, with only occasional freeze days, is kind to galvanized cable - corrosion isn't the main enemy the way it would be somewhere with hard winters. The real issue is age. A door built around 1990 is now past thirty years old, and thirty-plus years of daily cycling is exactly when factory-original cable starts to fray at the drum, even with no rust in sight.
Where it goes sideways is when a homeowner hears a snap, sees the door hanging crooked, and tries to force it open or closed anyway. That's how a cable job turns into a track and roller job. It also goes sideways when the opener has been fighting a bad cable for weeks before it finally breaks - by then the opener's gears may already be worn from straining against uneven tension, and that's a separate repair we can't fold into a simple cable swap. If the drum is scored or the shaft is bent, replacing just the cable won't hold; we'll say so rather than sell a fix that won't last.