Seems clear: if declarer knows he has the rest of the tricks, he is ethically obliged to claim only if he has no other motive to do so besides forcing opponents to think unnecessarily. If he thinks claiming will waste more of opponents' efforts, or that it will take longer to claim than to play the hand out, or opponents may be incapable of understanding the claim, or he wants a beer at trick 13, or even he just doesn't like claiming, he is allowed to play the hand out [though that last player makes my list of people to avoid, he is not unethical in doing so.]
J

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