In principle, you can even study while standing on one foot (Babylonian Talmud, Shabbat 31a).

What I mean is this: a bachelor’s degree in computer science, for example, is something that takes 3–4 years. Medical studies take 6–7 years, and so it is in every field of study—there is a time range it takes to learn it. If we relate to Torah as “study material” (though of course it is also holy) — how long should it take to learn all of it?

It depends on the learner. Rabbi Moshe Levi, author of Menuhat Ahavah (actually Rabbi Ovadia Yosef’s real halakhic counterpart), was appointed to a rabbinic position by Rabbi Mazuz already at age 21, and by age 25 had already published Menuhat Ahavah. And at 39 he passed away.

I’ll explain the Rabbi’s view (as I understand it).

A bachelor’s degree in computer science is defined because someone defined it. The Council for Higher Education set the list of courses and their content, there is an average level at which they are taught, and there is a number of courses a student can take in a semester, so it is easy to calculate.

If you had asked about rabbinic ordination, it would be possible to answer. There are a certain number of exams that have to be passed (Sabbath, niddah, slaughtering and checking, forbidden mixtures, etc.), the exams have fixed dates, and there are institutes that prepare students for them, and they can give an average preparation time for each exam.
The question is defined because it is clear what the scope of the material is, and it is clear at what level (the level needed to pass the exam).

By contrast, when you ask about knowledge of the entire Torah, including books of thought and midrash, at a deep level of understanding, the question is not well-defined, because it is not clear which books are included, and it is not clear what level of understanding is meant (and besides, there is not really anyone to ask).

Exactly so.
I’ll add one more point. Have you ever thought about why in every field it takes exactly three years to get a degree? Is it just a coincidence that the amount of material is identical in every discipline? Clearly, the degree was cut to fit, so that whatever takes three years is called a bachelor’s degree. And of course there are differences in what is done during those three years as well, but this is not the place.

And this brings to mind Rabbi Elyashiv’s puzzled rebuke to someone-or-other—I don’t remember who: “That all Israel accepted upon themselves to learn one page of Talmud a day, fine. But who decided that it’s an hour?!”

I just saw a reference to this topic—
the Talmud at the beginning of tractate Kiddushin says, “A person should always study Torah and afterward marry a woman,” and the Rosh [sec. 42] writes: “I do not know what the required measure for studying the entire Torah is.” So the above question is apparently unresolved.