The only artists I know well enough to comment on this are Ayumi, Namie and Kumi.
Ayu definitely does, she reinvents her style and her music constantly. Others may not think so but I think those people aren't actually listening.
Namie as far as I know only reinvented herself once. Since then it's been a lot of the same but don't get me wrong, it's gets better and better in my opinion. It's like she took something and stuck with it and keeps improving on it.
Kumi... I'm still waiting for her to reinvent herself lol.