There was a boy called up to the Torah as a bar mitzvah this morning in shul. My wife asked me an interesting question: would the bar mitzvah have to make a she'hechiyanu tomorrow morning when he takes his lulav and esrog? My peirush to question: even though the bar mitzvah boy has been doing the mitzvah of lulav from day #1 of the chag, that was a kiyum of the mitzvah of chinuch. Tomorrow will be the first day in which he is doing netilas lulav as a kiyum of netilas lulav. Would you say that the new kiyum mitzvah of netilas lulav obligates him to say she'hechiyanu even though it is the same ma'aseh mitzvah he has been doing all week?
[Update: take a look at the Tosefes Bikurim at the back of the Aruch LaNer on Sukkah, siman 637.]