Unlike other products, hairspray typically remains stable for a very, very long time. Assuming it’s kept in an area with a consistent temperature (not too hot nor too cold), commercial hairspray does not degrade quickly. A general rule of thumb is to use the product within 18 months. Interestingly, homemade hairspray recipes also last a very long time since they are preserved with vodka or in oil. Read each recipe carefully for the specific storage directions.