At some point, your furnace will become beyond repair, no matter how well it's maintained. Since winter came early this year, it's time to take note of the condition of your furnace and start learning about your replacement options so that when the time comes, you can make an informed decision. Here are some indicators that this may be your furnace's last winter. Age A well-maintained furnace has a lifespan of 15-20 years, on average. However, the cost of operation may go up