A lot of actors stay in character. Robin Williams, Johnny Depp, I believe Pacino and De Niro are known for it time to time and many, many more. The point of this is to be in character before the director says "action." To "be in the moment" as they say.
I have nothing to add about Carlito. Everyone has been saying the same thing about him for the last few months and in God knows how many threads. It's getting boring.