How long do garage door extension springs last?

Garage door extension springs typically last about 7 years, or roughly 10,000 cycles, where one cycle equals one full open and one full close. A household that uses the door four times a day will hit that 10,000 cycle mark in about 7 years. Heavy use, around eight cycles a day, can cut their life to 4 or 5 years. Several factors shorten their lifespan further, including humid or coastal air that promotes rust, doors that are out of balance and force the springs to do more work, missing or worn safety cables, and skipped lubrication. Extension springs reach the end of life suddenly, usually with a loud bang, so visible gaps or rust streaks are a sign to replace both at once.