[Avodah] tfillin check

[Rich, Joel via Avodah]

[RJR poses these questions at the start of his Audio Roundup column on
Torah Musings <http://www.torahmusings.com/category/audio>. I prodded
him to share them here as well, as questions work better in an actual
discussion venue. But I didn't think he would do so without plugging
his column! So, here's my plug: Worth reading, and if you have one --
pointing subscribing to on your news agreegator / RSS reader. -micha]

A Rav posted a shiur on the internet concerning what atonement is
needed by one whose tfillin were pasul yet were worn for years without
knowing this was the case. It was claimed that he thus never fulfilled
the commandment to wear tfillin. In fact, many pasul tfillin were pasul
from the start (e.g., missing a letter). The Rav later reported that a
listener heard the shiur and had his tfillin checked and found such a
psul, even though he had bought the tfillin from a reputable sofer and
had them checked earlier by another reputable sofer. The Rav was pleased
with this result.

Two questions:
1) Given that the listener had been following a (the?) recognized halacha
   by not checking them, is atonement (or not fulfilled status)
   appropriate?
2) As a societal issue, how should current rabbinic leadership view the
   tradeoff of now requiring (suggesting) frequent checks? We will have
   some who will have the listener's result. OTOH, we will also have
   those whose tfillin will more likely become pasul due to uncurling
   the klaf and the increased costs of checking.

BTW -- why didn't the halacha mandate this in the first place? What has changed and what might change in the future? Would constant PET scan checking be appropriate?

Kt
Joel rich