I hadn't thought about it until I saw how much dust gets stuck in the vents! It is usually recommended to clean the air ducts every 2-3 years, but if you have pets or someone who suffers from allergies, it is better to do it more often. I recently had an air duct cleaning Toronto done and was shocked at how much dust and debris had accumulated. After the procedure, the air in the house was much cleaner. If you don't want to breathe dust - don't put it off!