i know dave has had his like two years, sold it to his boss and bouthgt a new one. It's still running...
I t hink it might depend largely on luck and how often and far yuo run that battery down, liek any battery, drain it often enough, it ain't coming back.
See here for the new message that explains Apple's battery replacement policy, and see here for how long it took for the filmmakers to acknowledge that such a replacement program existed.