The Gemara tells us the requirement of checking a mezuzah:

The mezuza belonging to an individual is examined twice every seven years to determine whether it was stolen or became disqualified. And in order to avoid excessive burden on the community, the mezuza belonging to the public is examined twice in a fifty-year Jubilee period.

I would like to tell you a story from my personal life, actually two stories, about Mezuzos. Many people have the custom of checking their mezuzos if unusual and unfortunate occurrences happen in their home or to members of their family.

My reaction to this, being a rationalist influenced by Rambam and his approaches, is to understand the protective power of a Mezuzah as not coming literally from angels with wings that surround you. But rather, the awareness of G-d and the resulting spiritual attachment engendered by actually paying attention to the meaning in content of the Shema before leaving and entering your home.

Rambam excoriates those who treat mezuzos like a “good luck charm” (Laws of Mezuzah 5:4):

They, however, who write names of angels, holy names, a Biblical text or inscriptions usual on seals, within the Mezuzah, are among those who have no portion in the world to come. For these fools not only fail to fulfill the commandment but they treat an important precept that expresses the Unity of God, the love of Him, and His worship, as if it were an amulet to promote their own personal interests; for, according to their foolish minds, the Mezuzah is something that will secure for them advantage in the vanities of the world.

Here is what Rambam (Laws of Mezuzah 6:13 - is the number a coincidence?) says about how one SHOULD view the mezuzah and the statements of Chazal regarding its spiritual protection:

A person should pay heed to the precept of the Mezuzah; for it is an obligation perpetually binding upon all. Whenever one enters or leaves a home with the Mezuzah on the doorpost, he will be confronted with the Declaration of G-d's Unity, blessed be His holy name; and will remember the love due to G-d, and will be aroused from his slumbers and his foolish absorption in temporal vanities. He will realize that nothing endures to all eternity save knowledge of the Ruler of the Universe. This thought will immediately restore him to his right senses and he will walk in the paths of righteousness. Our ancient teachers said: He who has phylacteries on his head and arm, fringes on his garment and a Mezuzah on his door may be presumed not to sin, for he has many monitors—angels that save him from sinning, as it is said, (Psalms 34:8) "The angel of the Lord encampeth round about them that fear Him and delivereth them".  

However, after all of this fancy highfalutin philosophy let me tell you two stories. A number of people took illI at a clinic that I used to serve as Director.  Some of the religious employees were saying, “We should check the Mezuzos”. I scoffed and said, “Feh! Before you check the Mezuzos, check yourself. We should all have introspection into our deeds. We are more likely to find blemishes there than inside the Mezuzos!  But, if you really want to, ok fine we will check them.”

After all was said and done, the room of the clinician who took most severely Ill indeed had a mezuzah with a problematic letter.

Another event happened many years later. I am careful to check my Mezuzos is in my house twice every seven years as is required. It’s easy for me to remember because we moved into our home on Thanksgiving, so every three or four thanksgivings I go through the whole house inspecting the writings on mezuzos for any damage. 

It is somewhat time-consuming and so I do it over a couple of weekends. As I was going through the house over a couple of weeks, we had a number of mishaps: a flood in the basement, leaking gas, and another boiler malfunction. My family members kept saying, “See, you have to finish checking the Mezusos.” Of course, I scoffed, with my usual refrain of, do a self inspection better. 

Anyway, I’m embarrassed to admit that the final mezuzah that was checked did indeed have major water damage with letters at the top blotted out.

Forgive me Rambam, but I think I’m getting a little bit superstitious.