A new furnace can cost a lot of money, and it may also entail additional costs upon installation. But the thing is, you can actually maximize your money and extend the lifespan of your furnace if you learn how to properly maintain it. Generally, furnaces last up to fifteen years. However, if you make sure that your furnace is properly maintained, then it can last for up to as long as twenty years in average. Are you curious about how you achieve this?