I've been reading the "Theory of Poker", and the author writes that if you know that a person will never fold to a medium size semi-bluff raise, then its not worth making. This is b/c it eliminates 2 of the 3 reason to semi-bluff. But, what if you know that when you make your hand, he will most likely call your bet, even if its medium/large raise? This applies to NLHE tournament play.

It really depend on how well you know the player. If you think instead of semibluffing you can check and he will check everytime too, maybe taking a free card is the best decisiion.