"Serving your air conditioning and heating needs since 1959" – If a company makes this claim, they should be able to substantiate it. Ask to see their state license and see if the license was issued that long ago and if it is in the owner's name.
"We've been providing reliable HVAC service, repair and replacement for over 20 years." – Do they have one employee with 20 years of experience or 5 employees with 4 years each?