The original idea of the Litvak yeshiva was to be a four year program which would go through the three bava's [Bava Metzia, Bava Kama, Bava Batra] and four nashim [Gitin, Kidushin, Ketuboth, Yevamot]. This I see as very important even though it is not really the same thing as the commandment of learning Torah itself which applies all through life and is required of every man.
So the main greatness of the idea of the Litvak Yeshiva is that those are the ages 18-22 that a world view is formed. One generally accepts at that point the social meme of his environment at those crucial ages,- and this meme becomes hard wired. [So the idea in short is that you learn good morals at those few first years and that sticks.]
[This was the original idea of Rav Haim of Voloshin. Before that there was no such thing as a yeshiva in modern sense, but rather it was the local hall where people would pray in the morning, and then go off to their work. The younger people stayed there and learned. Then Rav Haim came to his teacher the Gra and suggested creating a yeshiva as an independent institution. It is not clear what the answer of the Gra was. There are different versions of the events. At any rate, I must add that I had a great time at the Mir in N.Y. And besides the my learning during the regular hours I also was privileged to spend time with Rav Shmuel Berenbaum (the rosh yeshiva that gave the highest class). He was a very deep and creative thinker along the lines of Rav Shach. But for some reason, he never wrote a word, and so most of his ideas were lost with time. Still you can get the basic approach from Rav Shach's Avi Ezri or Rav Haim of Brisk's books.]