Once a year you should get your Heating & Air Conditioning worked on.
For me, I do a twice a year cleaning.
I get the AC portion focused on in Spring plus the oil furnace in the fall. I have a central heating plus cooling device though. So it is a single plan that gets the maintenance on it, but for cooling, I get current refrigerant plus the fan blades checked. For heating it is all about the dust in the system. I entirely savor getting the twice a year cleaning to ensure my air quality is fresh. I also want to detach all the hair that gets in my system. I have entirely long hair plus I shed worse than any cat. I have to clean my dryer lint trap always. My tub drain needs to be snaked yearly. I also vacuum plus sweep to get the hair off my floors. An air filter should be able to last in a plan for around many weeks. With my long hair, 2 to 3 weeks is about all it can take. So I figure that normal people go a year with a single cleaning, I do 2 cleanings to get my hair detachd from it. The air filter doesn’t stop everything from getting in the system. I don’t want to have my long hair ruining parts in the Heating & Air Conditioning. I also get HVAC duct cleaning way more than any normal homeowner does as well. I don’t want dust, debris plus again, my hair clogging up the HVAC ducts. The plan of breathing in my old, dusty hair sounds disgusting.