It is a common misconception that the spring is the only important component in the torsion spring lift mechanism which enables the operation of the garage door. The other ones do an equally hard job. This mechanism consists of two types of stationary components and two types of moving ones.
The core stationary component is the cylindrical steel shaft. It is installed at a precise distance above the overhead door. At the two ends of the shaft, there are fixed drums. There is one lift cable attached to each drum. The bottom end of the cable is attached to the door. The spring goes over the shaft. Put the other way around, the shaft runs through it. The spring is loaded with force matching the weight of the door. This creates a balance and the door stays firmly in place when it is in a closed position. In this state, the cables are under a great amount of tension as well.
When the door opens, the spring unwinds and passes torque to the shaft and its drums. With the passing of the torque, the stored force is used for the movement of the door. The cables get rolled around the drums. During the closing process, the spring winds and gets loaded with force. The cables are released and lower the door.
Due to the fact that they are under great tension and work hard, the moving components of the torsion spring lift mechanism have a high natural rate of wearing. Eventually, they break. That is why both the torsion spring and the lift cables require regular inspection. If extensive wearing or significant damage is discovered, the affected components are replaced with new ones that have the same specifications.