in the thread "Mitzvah Kiyumit", R' Micha Berger wrote:
b- A mitzvah asei that carries no bitul asei if you omit it.
Tzedaqah (in most cases), tefillin, some claim yishuv EY
bizman hazeh, etc...
and later:
I think the bitul asei is only if one had a karkafta delo
manach tefillin. So, after one's bar mitzvah, there is no
bitul asei in omiting tefillin.
I've heard the phrase "karkafta delo manach tefillin" before, but in my
admittedly limited experience, it was always in the sense of "Oh, what a
shame! That head never got the spiritual benefits of tefillin even once!",
which is NOT that same thing as "That head still has a chiyuv of tefillin,
in contrast to others where tefillin is merely a kiyum."
R' Brian Wiener and I asked for more details, and RMB responded:
R' Saadai Gaon has a teshuvah about whether it's yuhara for
someone who learns all day to put on tefillin, given that
most people around him didn't.The Semag (asei #3) mentions the neglect.
Also, Tosafos (Shabbos 49a, "keElishah").
Even as late as the Kol Bo... The BY (EhE 65) quotes the KB
as suggesting that the reason why some chasanim don't put
ashes on their head is because the minhag didn't take hold
or perhaps faded away in communities that don't put on tefillin.
I have not seen R' Saadia or the Semag, but I did take a quick look at
Tosfos and the BY/KB. Neither one says anything even remotely similar to
Tefillin being a chiyuv only once. They do bemoan the prevalent laxity in
tefillin, but that could easily be due to people wearing them only for
Shacharis rather than all day.
Alternatively, it might be that tefillin was neglected entirely by many
people in those communities. The sociologists among us can probably come up
with more examples, but I can recall shaatnez being referred to as a "meis
mitzvah" because it was so widely ignored, and I can easily imagine that
other mitzvos suffered this fate in other times and other communities. Some
would say that women's hair covering was in this category for a long time,
and I'm wondering if tefillin might have been too.
In any case, citations about communities not wearing wearing tefillin is
not a proof that the tefillin did not need to be worn on a daily basis.
Akiva Miller