I have heard that a m'zuza must be checked twice every seven years by a qualified sofer. I have also heard that, assuming it's known to have been kosher at one point, it need only be checked for faded ...
May one use mezuzot with different scripts in the same house? For example can the muzuzah in one room be ashkenaz (beit yosef) and in another be sefardi (vellish)?
What ingredients are currently used in the manufacture of ink for Safrus? Is there a different formulation for the paint that is used to dye tefillin straps/boxes?
Can a women write a Mezuzah?