During the heating season, there is never a convenient time for a furnace to split down, especially considering the discomfort & hazards of leaving a home unheated.
There is no such thing as a furnace that never dies.
They regularly last about 15-20 years. There is no way to suppose its expiration date in advance. All you can do is exercise caution as the furnace enters the final quarter of its life, knowing its age may help put any performance problems in context. As the furnace is a single of the largest energy consumers in modern homes, its efficiency level directly affects your bottom line. If you are paying much more than last year & the rates have not risen, your furnace needs attention. Depending on circumstances, service may be able to give an efficiency boost. Feeling cold indoors even though the heat is on provides perhaps the most evident motivation for taking a close look at your furnace. Bring in a professional, especially if you notice significantly unusual temperatures in unusual rooms. Uneven heating may be the inevitable result of an decreasingly outmoded technology. Your furnace could not be doing its task to remove airborne particles from the warmed air. First thing to do is check the furnace filter & clean or substitute it if necessary. If it’s been years since you changed your filter, or if it’s never been changed, permanent mangle may have been done to internal furnace components. Sometimes, sitting next to your furnace can tell you a lot about its condition. Check for corrosion & cracks, & in the process listen for any unfamiliar sounds. While squealing & screeching are a clue that the blower may need adjustment, other types of noise prefer grinding & banging, indicate the need for either service or full substitutement. Also, pay attention to how the furnace room odors. When you start up the appliance for its first use of the season, you can expect a musty odor, however if the odor lingers for more than a few days, schedule a service appointment immediately. If the furnace cycles on & off frequently or if it runs all of the time, it’s a clear sign of the furnace not working as it should & it’s time to substitute.