Until they start squealing and you have to send them in for repair. Lather, rinse, repeat, as Frank noted. It really is s shame as when they're working they're the best bargain in stat headphones, IMO. I still flirt with picking up a pair when a used set comes up in the "reasonable" price range but always back away when memories of the issues return and I remember the rumors that Koss will now only provide warranty service for the original owner.