I've personally had the same battery in my razr for 1.5 year and never once thought to buy a new battery even when the talk time suffered.
Now I consider myself a more educated cellphone user
u think avg joe user will give a shit to think about buying new batteries let alone care enough to?
hell new cellphone batteries are expensive if you dont know where to get em, especially from all these retailers that sell you cheap ass fake batteries for fuckin $30+++