For really hard core Litvaks, there is almost no value in learning unless it is learning in depth. This I saw in Shar Yashuv in particular, But at the Mir and many other Litvak yeshivot, the afternoon is devoted to learning bekiut [fast learning].  So as a compromise, I learned every paragraph twice and went on. After all, I had not the intellectual tools to go in depth.  But eventually, I found myself learning with David Bronson in Uman, and his natural ability to see into the depths of Tosphot and the Gemara opened up for me the whole concept of learning in depth. But my learning with him came to an end. 

 For many people like me, I think the best thing is the combination of having some session in depth [review ten times of every thing, and learning the rishonim/early authorities and achronim/later authorities on the sugia (subject)] and another for fast learning. 

Also I would like to add here an idea that the real learning comes by listening to an expert. Rav Nahman brings this idea based on a Midrash that says this: Klal Israel [the House of Israel] at Sinai when offered the commandments said, "We will listen and do." But later they made the Golden Calf. Then God now says to us :"You have lost the we will do. So now at least hold onto we will listen."  Now Rav Nahman explain that saying the words yourself is "doing." But  we have lost that. That means learning yourself is not very effective.  Effective learning happens only by listening.