Any pillow is best replaced at the latest every two years, and often every year. Your pillow becomes contaminated with skin cells, skin and hair oils, make-up, possibly dust mites and saliva. It is healthier to replace it annually for that reason alone. However, many pillows begin to break down in quality and lose their cooling capability over time. So once a year we would recommend. If you have a removable and washable cover, this could be extended to 18 months to two years at a push – but you should be able to tell when it needs to be renewed.