The life of an earthing sheet depends on its use, more specifically the washes and the degree of perspiration. If you wash your grounding sheet monthly (when using your own top sheet, this can be done monthly depending on how much you perspire) then they will last for a minimum of 2 years (3 years is normal, 4 years is possible), with sufficient grounding efficiency for your body. Then the conductivity can decrease.After 2 years, or if you are in doubt (e.g., in the event of a wrong wash), it is best to check the conductivity of your sheet with the product tester if everything is still OK:https://www.aarding.org/products/testerWash regularly to remove the salts from your perspiration that are buffered in the cotton before they can oxidize the silver.An earthing sleeping mat has a longer lifespan because it does not depend on correct washing and possible oxidation.