The lifespan of a furnace ignitor can vary depending on a number of factors, such as the type of ignitor, the quality of the product, and the amount of use the furnace gets. In general, a furnace ignitor should last for several years before it needs to be replaced. However, some ignitors may fail sooner, especially if they are of poor quality or if the furnace is used heavily. It is important to regularly inspect and maintain your furnace to ensure that all components, including the ignitor, are in good working condition. If the ignitor fails or shows signs of wear, it should be replaced to prevent furnace problems and ensure that your heating system is operating at peak performance.