If you don't take care of it now, it will take care of you later $$$$$.... Turning the thermostat on is all that is needed for cool air, right? Likely not, if you have not maintained the HVAC system year round. Neglegence or ignorance is usually the culprit when an A/C system is malfunctioning. Whether it is: overgrown vegitation at the compressor unit, weedeater damage to the fins, dryer lint release outlet to close to the unit plugging the fins, a lack of fin bathing (at east annually), lack of timely filter change (different for each type of filter) or plugged condensation lines causing rusted drain pans and rusted furnace cabinets, if not addressed as regular maintenance, these listed items can cause system failure. Encourage your clients/contacts to take the time and the FEW dollars necessary to save MANY more dollars later. This does not even address the issue of inconvenience when the system goes down. I spend a good deal of time with each client educating with regard to systems maintenace in the home to protect them into the future. I think it is part of what we should do as professionals.