Someone told me that people avoid wearing tefillin all day because of the fear that one might denigrate the tefillin by passing gas with the tefillin on. If someone feels that he is capable of keeping a clean body throughout the day (not passing gas) or removing the tefillin before passing gas would it be OK for him to wear tefillin all day long?
Rav Eliyashiv was asked this and was qouted in Sefer Vayishma Moshe 2: Teffilin. He was asked if there is an inyan to wear talis and teffilin all day. He answered that a talis it isnt necessary since one wears a talis katan,and regarding teffilin a person needs a guf naki. He was then asked if one knows with certainty that he will have a guf naki is it them an inyan to do it. He answered "Halevei" that one can do such a thing and if one can do such a thing then a bracha should be upon him.
side question: why isnt this mechzei k'yuharah?
דעת הגאון מוילנא, הובא בספר כתר ראש לרבי חיים מוואלוז'ין ובספר מעשה רב, שאדם שיכול לשמור את גופו נקי צריך להניח תפילין כל היום, ואמר הגר"א שאם היה לו כח היה יוצא בשווקים וברחובות לעורר אנשים לעשות כך. אבל גדולי הדורות לא נהגו כדבריו. תורגם ע"י התרגומון של גוגל
The Gaon of Vilna reported that a person who can keep his body clean should wear tefillin all day long, and the Gra said that if he had the strength he would go out in the markets and streets to make people do so. But the great rabbis did not follow his example. Translated by Google Translator