As long as one offers variety and versatility, there is no problem. But type cast things are really boring. My comments are about films only. I never watch any T.V serial. If I am not tied to post to see the serials, I will not see any.
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It depends on the strength of the serial's story like Humlog, Buniyaad, Tamas and on the person like Aloknath, Reema lagoo - Drama
Knowledge and how he carries with audience and competitors like Annukapoo or Sonu nigam aka sonu niigaam (Saregama) - Singing
How interestingly they carry Siddarth / Derek (Quiztime) - G.K based
Spontaneity of person like Amithabh - KBC
Same cannot be said about few like Mandira Bedi (who started with Shanti) who tried everything she can (and producers / tv channels)
Some time its surprising to see how they change (Sudha chandran from Nachi Mayuri to k'serials