Cong. Shomrei Torah of Fair Lawn Tefilin and Mezuzah Checking Sunday, December 3
People tend to notice if there is external damage to their tefilin such as splitting of the Bayis or brown Retzuas. This does not require an internal check. We recommend internal check no more than once in 15 year
Mezuzas have a mandated check of twice every 7 years as mentioned in Mes. Yuma י'א and שלחן ערוך יו'ד רצ'א
Mezuzas that are not in use should not be checked. They should be sent along as backups in a separate bag with a note stating they should be used for backup in the event that one of the other mezuzas needs to be replaced.
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