The most crazy secret is your furnace can last as long as you want it to! What we mean is, there is not date when a furnace needs to be replaced. People can simply fix what's wrong. But here's why that may not be a great idea:
There are two primary reasons that people replace their furnace systems.
1. It's not safe to operate.
2. It's not practical to repair your furnace (it's no longer reliable, it's too expensive, etc).
3. It leads to high energy bills
There are some scenarios where repairing your furnace is not practical. For example a furnace with a cracked heat exchanger will still function, however deadly gas will be leaking out into your home.
Your furnace may also be at an age where parts are continually breaking down making it unreliable. During winter, frequent repairs can cost more than a new system and will be definitely more tiresome.
Benefits of replacing my furnace?
1. Efficiency: Older furnaces simply don't heat as effectively as a new one.
2. Cheaper utility costs: The more efficient a furnace, the cheaper it is to run.
3. Programmable thermostats: These offer more control settings, quieter operation and save you money when you aren't home.
4. Piece of mind: Knowing your furnace won't break on the coldest day of the year has value.
So, you take care of it, do routine maintenance, and continue to fix it, you can theoretically make a furnace last a lifetime. But sometimes, the best course of action is to make safety and piece of mind a priority and decide to just get something new.