I ' m a shitty human being for using Tor ? Very well then . <| sep |> It depends completely on the specific chemistry . Liion can be made to last a long time otherwise they would be pretty pointless to put in an EV , wouldn ' t they ? , but short of finding a teardown of one and finding the data sheet of the battery that tells you that information , you aren ' t going to know that . I wouldn ' t read too much into the toothbrushes that lasted a decade . That sounds like a classic case of survivorship biassfla 1 . You ' re just not seeing the ones that failed a long time ago . In any case , I have to agree with upetyper . I can ' t think of many places that use nimh anymore because it ' s more expensive and difficult to work with than liion . It ' s almost certain you will get a liion model unless you are getting an old model or something .