Q. My large family resides in a sizeable house that has close to fifty mezuzot. To have them all checked every three years and a half is difficult and costly. I heard that if instead you check just three different ones on each occasion, it is enough since you have created a proper chazaka. Is that correct?
A. Birkei Yosef (Y.D. 291: 1) rules that just checking three does not suffice, since not all locations are similar and comparable.
See however question (3036) above, where we mention that Horav Shlomo Miller Shlit’a maintains that mezuzos that were checked properly when bought and they were placed in transparent glass tubing containers where one can clearly see that even the plastic they are wrapped in, is sealed and intact, one does not to check them every three and a half years,
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a