Maybe you grew up in a home where rarely used rooms were closed off and vents were also closed in those rooms. You may have been told that this would save the money. The truth is that the practice of closing vents actually harms your furnace.
Closing vents creates back pressure on the system. Furnaces are chosen and installed depending on the square footage of your house. Changing the output by closing vents means that your system is not operating optimally. Your system needs the proper balance of supply and return air, otherwise it will have a shorter lifespan and you will need to replace it sooner than expected. You will also have improved air circulation and it will actually lower your utility bill because it won’t be causing stress on your system thus overworking it.