The most common call we get from this part of our service area is a door that won't open at all, paired with a loud bang from the garage sometime beforehand - that bang is the spring letting go, not the opener failing. Garage door openers are built to stop pulling once they sense resistance, so after a spring breaks, the motor usually runs but the door barely lifts, or the opener reverses itself immediately.
A second, quieter symptom: the door feels heavier than it used to when you lift it by hand with the opener disconnected. That's a spring losing tension gradually rather than snapping outright, and it's worth a call before it fails completely and takes a cable or bearing with it. Either way, the fix is a spring replacement, not an opener repair, even though the opener is usually what gets blamed first.