Lifespan depends on use. Typically, average use is about 2-4 months per pair of tips. How you use the tips, body chemistry (earwax, oils, etc.), and environment all effect how long your tips will last. To make your tips last the longest, make sure to always "prep the tip" (compress the foam before inserting them into your ears), clean your tips occasionally, and store the tips and earphones in a case while not in use. Replace your tips when they start to "flake", tear, or lose their memory foam properties (for example, the foam expands quickly rather than slowly).