Your system will last longer the better you care and maintain it. If you have your HVAC system, exhaust fans, and range hood vents cleaned and checked regularly, they will last 20 to 40 years or more. If you don't keep them cleaned and maintained and if your system is too small for your kitchen, your furnace, air conditioner, and fans can give out in as little as 5 to 10 years. You should also consider having your ductwork and exhaust duct systems cleaned and checked on a regular basis.