According to Jewish law, the Shulchan Aruch (YD 291:1) states that a mezuzah placed on private property, such as on one's home, must be checked twice every seven years (i.e., every 3½ years). The Mishna Berura (39:26), quoting the Magen Avraham, advises that tefillin should also be checked twice every seven years. In fact, many rabbinical authorities today recommend that even high-quality tefillin batim be checked annually.