After discussing the laws pertaining to the synagogue, the Shulhan Aruch (Orah Haim 155:1) discusses the obligation of Torah study. Specifically, one must establish a set time to learn Torah daily and one should not pass up this set time even if there is potential for great financial gain. The Kaf HaHaim (O.H. 155), quoting Rabbi Avraham Azoulay (Hesed LeAvraham), compares Torahstudy to the Tamid offering; just as this sacrifice was a minor one but was offered twice daily in a consistent manner, so too Torah study should be consistent. It would appear from the wording of the Kaf HaHaim, that what is important is not the amount of time spent studying, but rather that whatever time is dedicated to studying should be done consistently. Furthermore, the Mishna Berura (O.H. 155:3) writes that people who work should not focus whatever time they have available solely on Gemara, but should study the works of the Poskim (Halachic decisors).
Interestingly, it is said of Rabbi Efraim Margoliot, that although he was successful in business, when he entered the study hall he would consider himself “dead”. In other words, he was so focused on his set time for learningthat it was as though he was dead to all worldly matters. This is in line with the Talmudic dictum that the Torah is only acquired by one who kills oneself, as it were, for the sake of learning (Berachot 63b) . Additionally, the Gemara (Shabbat 31a) explains that one of the questions that one will be asked after one passes away is whether one had a set time to study Torah.
Summary: What is of importance regarding the principle of setting a timefor Torah study is not necessarily the amount of time spent learning, butrather that it be conducted diligently and consistently.