I occasionally check very old Tefillin Parshiyos. They usually were a yerusha from the zaide to the grandchild. These old parshiyos are often in bad shape (and there is only so much a magiah can fix).
I sometimes feel to let the tefillin owner know that he should possibly switch to a new pair since there are many "issues" with the Tefililin, although kosher. I notice that some people are annoyed at even hearing that the Tefillin are anything but perfect, basing it on the fact that their zayde was so holy...
The question if they think they are wearing halachikly mehudar Tefillin and to my opinion in its current state it is not mehudar, how to address this sensitive matter.
Side question, I found parshiyos wrapped in synthetic string, (since sayros are halacha moshe msinai), is there anything to be concerned with the parshiyos (the ksav is not nice but basic kosher)?