No flames here... you have made some good points and I agree.

Two things about the HVAC filter...

- it could be tricky the first time you do it yourself, but after you've done it once it's a piece of cake.
- I live in a dusty area and keep my AC on recycle mode. I changed the filter at two years and 24k miles. It wasn't that dirty and I'll go maybe 3-4 years before I change it again.