The answer to 'how often to replace emergency HVAC service' is that there is no set schedule for replacing emergency HVAC service. Emergency HVAC service refers to the repair or maintenance of your heating, ventilation, and air conditioning system when it unexpectedly breaks down or experiences a problem. The need for emergency HVAC service can vary greatly depending on the age and condition of your HVAC system, how well it has been maintained, and the specific issue that has occurred.
In general, it's a good idea to have your HVAC system inspected and serviced by a professional technician at least once a year, typically before the start of the heating or cooling season. This can help identify and address any potential problems before they turn into an emergency. However, unexpected issues can still arise, and you may need to call for emergency HVAC service at any time. The key is to be proactive about maintenance and to address any problems promptly to avoid more costly or extensive repairs down the line.