HVAC Maintenance Contract

I recently bought a row house with central AC/heat supplied by an air handling unit on the roof. The previous owners had an annual maintenance contract with an HVAC company and the company came 2x year to check on the unit and whenever there were maintenance issues. Is it necessary to have the AHU checked every spring and fall? While it seems very prudent to do, I am not sure if it’s needed. Though having a professional who knows the unit is probably good in case of emergencies.