I like the bi-annual service plan, where my home unit is checked at twice yearly. My older HVAC unit came with my home I purchased in 2001. Knowing this is older technology, I wanted to keep it up to par, and Mack Heating and Cooling has done that very well.
I used a prior company, and they were always telling me I needed something new. Mack Heating and Cooling is far more fair in their aiding to maintain the existing unit.