The answer to 'how long does furnace last' is that a well-maintained furnace can typically last 15-20 years. The lifespan of a furnace depends on several factors, including the quality of the equipment, how often it's used, and the maintenance it receives. Proper maintenance, such as annual tune-ups and filter changes, can help extend the life of your furnace.
Older furnaces may start to lose efficiency and require more frequent repairs as they age. It's generally recommended to replace a furnace that's over 15 years old, as newer models are much more energy-efficient and can save you money on your utility bills in the long run.