Often tefillin are passed down the generations. It’s more necessary and meaningful than a wedding band. It’s a big deal, to say the least.”
I am not sure they now can be handed down generation to generation. While the Battium are now mostly made of cow hide and can last for long time if left in a car can warp making them not kosher. The Klaf that the parshas are written on now is very thin and have a life of 30 years so the ink may crack making it not kosher. The tefillin needs to be checked and if there is a problem with one of the parshas they all must be replaced. Older Klaf is thicker and the ink doesn’t crack as easily. Don’t rely on me ask a Jewish scribe he will tell you the same thing.