In most cases, your furnace or air conditioner should last between 15 and 20 years. However, this is largely due to the maintenance on the equipment, the overall quality of the brand, and your entire home’s performance. If you have a brand new furnace, but poor ducting, you may experience high static pressures within your ductwork. High pressure could cause air leaks, unit cycling, and efficiency drops. Just like a car, it is best to run your equipment continuously. If you notice that your system goes on and off constantly, it may be time to look at your ductwork, insulation, or ventilation in the home.