How long should my HVAC system last? February 24, 2011 — Art Avent, hvac advice. Among manufacturers, you are unlikeley to find anything definitive in writing on this question, but my personal opinion is that an electric heat pump & air conditioner SHOULD last 12-15 years & a gas furnace SHOULD last 15-20 years or more. Truth is, they last anywhere between 1 – 20 years.