We are called upon to repeat the study of the same tractate over and over again.
It is not that we are asked to learn it by heart, for even if we know very well every word and letter, we are still asked to study it again.
Some of the greatest Jewish scholars, among them the Vilna Gaon and the Rogatchover (Rabbi Yosef Rozin of Dvinsk), had eidetic memory: they retained each and every word and sentence they ever studied — and yet they never ceased to study.
These scholars went over the same books time and time again, because every new cycle of study reveals new aspects of the Torah, facets that can be revealed only in the second, or 100th, time.
This is why whoever finishes studying a tractate promises to repeat it again and again, regardless of whether he knows it forward and backward or whether he does not really remember it all that well.
Thus, every finishing point of whatever part of the Torah is only a “recess.”
After a certain point, one must once again start studying everything from the very beginning.
–Rabbi Adin Steinsaltz