As a homeowner and someone who works for an HVAC contractor, the single most important advice I was given is to have routine annual maintenance performed by a professional HVAC contractor. These are the reasons why, 90% of furnace breakdowns are preventable with routine maintenance. Manufacturers are becoming increasingly stricter when it comes to warrantying failed or defective parts. They want proof that the unit has been maintained. Routine maintenance prolongs the lifespan of the furnace. Saving you from having to make costly repairs that could have been avoided or under warranty had maintenance been performed. Basically having a professional perform the routine maintenance is a cost upfront, but it will save you money in the long run and keep you safe and comfortable.