You should have a regular tune-up twice a year, typically at the beginning of each heating and cooling season, to ensure that your system is working efficiently before the weather gets too hot or too cold. However, maintenance may be scheduled at any time.
Extended warranties and service agreements do not cover the cost of regular heating and air conditioning maintenance. Tune-ups are considered regular maintenance and are required by most manufacturers for your warranty to remain in effect.
Home depot is running a special on AC tune up service for $29 usually it cost $79.