Here’s another thing I had been assuming and it turned out not to be 100% true. As a person with a wide range of allergies, I believed I was doing only good by using the highly rated and very dense air conditioner filters that catch almost everything.
When I had the ducts cleaned, the tech pointed out how hot the air handler was. He said that when it has to pull air through the very dense super filters, it works much harder (and thus uses more electricity), runs hotter, and shortens the life of the air handler.
The super filters cost many times more than the simple ones. By using the simple ones I’ll save on air filters, save electricity, and potentially save on not having to replace the air handler sooner than necessary.
What really helps my allergies is having the ducts cleaned. I have to do that at least every two years, or I notice much more allergy trouble. I don’t notice that much difference with the filters.