Just performed a Routine Maintenance & Tune Up on a Carrier Natural Gas Furnace in Wilmington Delaware. Everything was looking perfect after adjusted their gas pressure slightly. It looks like the filters are continuously changed and around the unit was looking pretty spotless already, which extends the life of any unit. Mostly the filter, but keeping a clean unit can make spotting issues waaaayyyy easier. Thank you Mike and his family for trusting us and allowing us in your home. Happy Holidays