The answer to 'how often to replace HVAC system' is that most HVAC systems should be replaced every 10-15 years, on average. HVAC units have a finite lifespan, and over time, they become less efficient and more prone to breakdowns. Replacing your HVAC system before it completely fails can help you avoid unexpected and costly repairs, as well as reduce your energy bills with a more efficient new system.
The exact lifespan of your HVAC system will depend on factors like the quality of the equipment, how well it was installed, and how well you've maintained it over the years. Proper maintenance, such as regular tune-ups and filter changes, can help extend the life of your HVAC system. However, even well-maintained systems will eventually need to be replaced.