It's not seasonal at all and HVAC shops are far more comprehensive than just Heating/Cooling. V is for ventilation so any ventilation system consisting of blowers, fans and ducting is included. Air Conditioning is understood to be cooling but those systems range from window units to massive chiller systems. They can also service refrigeration systems for commercial and industrial use.

At work we had an out of warranty water chiller for a laser break down so we called our HVAC guys who found the leak, patched it and recharged the system same day.