Tefillin and Mezuzot could become un-Kosher due to change in temperature or humidity, as well as other factors. The law is that Mezuzot need to be checked twice each seven years, Tefillin instead are required to be checked if not worn regularly or if they could have become not-Kosher due to factors like high heat, humidity, etc…
Rabbi Lazar has helped countless people with their Tefillin and Mezuzah checking, either by sending them to a Sofer (expert scribe) or by bringing the scribe to Rome.