Our Heating.AC company had a twice a year plan for $119.00, we would get priority if we needed service call, saved a few percent on any parts needed. Their yearly check of furnace/AC at their convenience, not ours. We both work together and ride together and couldn't get to work for a couple hours or more after we opened the doors. We dropped them and now will take our chances when service is needed.
I think it is just another way for them to make money. Cleaning furnace-AC is not rocket science, we do our own now. We change filters every 30 days.