In Talmudic times, it was common for one to wear tefillin all day long. As the Torah does not limit its observance in any way, there would seem to be no reason to limit time spent wearing them to a few minutes a day. Even the exemption from wearing tefillin at night and on Shabbat is subject to much Talmudic dispute, with many asserting that Shabbat z’man tefillin hu (“Shabbat is a time for [the wearing] of tefillin”).
One of the key components of the legal discussions of the Talmud is the bringing of proof texts to support a given position. At times, the proof texts are from the Torah; at times from Nevi’im; and at times from Ketuvim. At all times, they lend authority to a stated position.