The average lifespan of ductwork can vary depending on a variety of factors such as the quality of the materials used, the level of maintenance it receives, and the environmental conditions it's exposed to. Generally, well-maintained ductwork made from high-quality materials can last anywhere from 15 to 25 years, while poorly maintained or low-quality ductwork may only last 5 to 10 years. It's important to have your ductwork inspected regularly by a professional to ensure it's functioning properly and to catch any potential issues before they become major problems.