Your garage door more than likely operates with torsion springs, though there is another kind of spring that could be supporting your door. These springs are heavy duty, and under a lot of tension. If one breaks, there is potential for serious injury, and damage to the garage door.
There is no definitive answer to how long your torsion springs will last. With proper care and garage door use, they can last several decades. When shopping for your new garage door, look into the warranty on the springs.
If a spring breaks should I replace it myself?
No! Even the most experienced do-it-yourselfers leave this job to the professionals. Because of the tremendous amount of tension these springs are under, if it causes anything to fall, you could get seriously hurt, or killed, in the process.
A professional can replace your torsion springs in a little over an hour. Most of the time is spent removing the broken springs, with only a few minutes required to install the new ones.
If one breaks, replace both, because the other one won’t be far behind it. The professional will be able to tell the correct size of springs much easier than you will be able to.
What takes a professional about 75 minutes to accomplish could take you hours, or even days. Leave the complex jobs to the professionals. If you cannot afford to have the repairs done right away, stop using the garage door completely until you can.