Helen thinks royal names get retired because someone has been spectactular. Akcherly, it seems that names get retired if the last holder was so despicable no one wants to use it again, like Richard and Henry (or less well known, Maude and Stephen). There hasn't been a Richard since Crookback, or a Henry since He of the Wives, and this in spite of the fact that Henry is tied with Edward for most popular so far. I think the presumption is that if Charles manages to outlive his mum, he will be Charles III. He's in the unenviable position of Eddie VII who was well into his 60's when Vickie finally pegged out, and he didn't reign very long.