There is a tremendous benefit from learning mishnayos, because they are the basis of the Oral Law. We have a tradition that the father of the tribe of Asher is especially responsible for those who learn mishnayos (as it says, ‘Asher’s bread is shmena’ which are the same letters as Mishna), and he does not let someone who learned mishnayos enter gehinom.
If a person wants to learn something by heart he should heed our Sages advice and learn just a small amount again and again until he has acquired it completely. He should not aspire to memorize too much at once, but rather should set aside a time once a week, besides his regular learning sessions, to memorize one daf gemara or one chapter of mishnayos. He should then repeat it again and again every week until he has acquired it completely and only then learn more. Over time he will acquire a vast amount of Torah he knows by heart.
To avoid forgetting what he learned, he should repeat it regularly when he has time, or he should repeat it after eating and before bentching, to elevate each meal with Torah.