I think it happens to most actors in great long series roles.
Michael Imperioli will always be christopher. its happened to a lot of the wire actors and It'll prolly happen to a lot of the breaking bad cast
I think Bryan Cranston will be safe from that. People thought he wouldn't break out the role of Hal the outrageous dad from Malcolm In The Middle. He flipped that shyt when he became Walter White and when I see him in recent movies I don't think "it's Walter White! " but rather "Oh shyt! Bryan Cranston! "