If you have never had your Mezuzot or Tefillin checked, it is a good idea to do so. In fact, Halacha (Jewish law) recommends to have Mezuzot checked approximately twice every 7 years.
Why? Like Torah Scrolls, properly written Mezuzot and Tefillin are written to very exacting standards. Every letter and word must be clearly written in a very precise manner. Over time it is possible for letters to crack or fade, or even for ink to run, which can invalidate the item until repaired (when possible).
Rabbi Lewin, an expert Sofer from NY will be coming to Houston next week (checking fee: $70 Tefillin, $8 Mezuzah). If you would like to have your Mezuzot or Tefillin checked, please contact Rabbi Schmukler by this Sunday/Monday to arrange it.