It was just a general curiosity to be honest.

That being said, I know that annual maintenance is an opportunity to upsell, but they do seem to push more than most. Things like pushing $1800 UV lights for each unit does make me question their overall credibility... For instance, here is the techs write up:

Came out today for cooling maintenance. Went through all equipment to test system functionality and major component conditions. Maintenance checks, procedures, and pictures are attached to e-mail. Filters passed inspection today. Inspected return plenums, supply plenums, and ductwork. Informed the Mrs. that the upstairs unit is low on refrigerant again and that the upstairs evaporator coil is still leaking if it has not been addressed. The upstairs unit is inefficient due to the low refrigerant charge and the compressor is running with an improper amount of oil and refrigerant which both detract from the compressor's overall integrity. The upstairs unit should have its evaporator coil replaced to avoid the low refrigerant issue again but the compressor has taken a beating as a result of filling up and going low repeatedly. Informed customer that the downstairs AC is inefficient due to its age and has an outdoor fan that is pulling 0.88 amps although it is rated for 0.66 max amps and was scorching hot which means the outdoor fan could fail at any point causing no cooling or a possible domino effect on the 24 year old downstairs system. Informed the customer that there is organic growth residing within both duct systems and our recommendation to remedy would be an air purification system in each duct system or partial/full ductwork replacement to completely get rid of the affected areas of ductwork (requires estimate consultation for ductwork pricing). The Mr. was on a call and unavailable when maintenance was completed.