The answer to 'how often to replace ductless system' is that ductless mini-split systems typically last 10-15 years with proper maintenance. However, the lifespan can vary depending on factors like usage, environment, and maintenance. Replacing the system may be necessary if it becomes less efficient, develops major issues, or no longer meets the home's cooling/heating needs.
Regular maintenance like cleaning filters, inspecting refrigerant levels, and addressing any problems early can help extend the life of a ductless system. It's recommended to have a professional HVAC technician service the system annually to ensure it's operating safely and efficiently.