During the critical repair window, HVAC systems can reach 20 years of reliable operation

https://precisiontrainedhvac.wpsuo.com/running-an-hvac-system-past-30-years-multiplies-failure-risk-and-replacement-cost-exposure

A typical HVAC system operates effectively for 15 to 20 years, but that lifespan depends heavily on how quickly you address breakdowns when they occur