What are your thoughts about saying shehechiyanu for occasions not mentioned in Shulchan Aruch? For example, can it be recited by parents at shul for the 3rd birthday of a child whose wimpel will be used for gelilah. What about other lifecycle events such as benei mitzvah, or weddings?
There’s certainly simchat ha’lev, which SA OH 223:4 says is the underlying basis for making the berakhah, but on the other hand, are we makpidim (particular) not to extend the berakhah into other experiences?
The first big question here is weddings. Why is there no standard practice of shehechiyanu, given that it is clearly a time of joy?
My general take has been that the sheva brakhot are an expanded and more specific version of shehechiyanu, so there is no place for the more generic one. However, it has occurred to me that in the past weddings might have been more financial, and societal arrangements without as much simcha, so maybe the association with simcha is more pronounced nowadays. In the end, though, I do not believe that that is a sufficient explanation of why there is no shehechiyanu. Nissuin is always defined as a time of simcha in multiple areas of halakha (see for example – אין מערבין שמחה בשמחה, לשמח חתן וכלה, אין נושאים נשים ימי הספירה, וכו.) Therefore, I believe the reason for omitting shehechiyanu is that Sheva Brakhot essentially embody an intensified form of shehechiyanu, rendering the more generic version redundant.
As to other occasions – the general practice is not to recite shehechiyanu for the occasions you mention. I think it is less (or not only) because it is not written in Shulchan Aruch, but also because these birthdays happen automatically, and there is no particular simcha of “Thank God we have finally arrived at this time.” There are achronim who discuss making a shehechiyanu for a person’s 60th or 70th birthday (some say to play it safe and have a new fruit / new suit; others do not require this) – but that is because that is (or was) considered to be a major accomplishment that could not be taken for granted. (See Kaf HaChayim 223:29 and Chavot Yair, 70).
The difference between birthdays of these ages and 3rd year birthdays or bat/bar mitzvah makes a lot of sense to me, so – without a new fruit, etc. – I would not make a berakha on those occasions unless there was a particularly strong felt sense of simcha. See the Bach (OH 29 end) who writes that because it is about simchat ha’lev it can be made even when there is some sense of this simcha – which allows for perhaps greater leniency.