I recently attended a college graduation, and one of the parents decided to recite shehecheyanu to celebrate the occasion. I have never heard of someone doing this -- is there any basis for saying it? ...
The Rambam writes in Sefer Ahava - Hilchos Berachos - Halacha 9: That Shehecheyanu is recited for every mitzvah that involves acquisition of property: I.e. Mezuzot. ט כל מצוה שהיא מזמן לזמן כגון ...
Say you bought a nice suit. Can you say shechechiyanu on it if there's a possibility that you might return it. If you already did say shechichiyanu on it, are you allowed to return it?
It is a rabbinical mitzvah to make eruv tavshilin, it even comes with a blessing. If so, why don't we make a shehecheyanu on it?