I knew Rav Lichtenstein zt”l well, and heard hundreds of shiurim from him. Others heard thousands, I only hundreds.
One short story. Almost half a century ago, A talmid of his, now a renowned Rosh Yeshiva, was astounded at how much Torah Rav Lichtenstein knew at such a young age, and asked him how he managed to know so much so early in life. Rav Lichtenstein answered, ” When I was younger,I slept only every other night. One night I slept, next night I learned all night, etc…”
Combine intellectual genius with unreal hasmadah, an unparalleled power of concentration, tzidkus and anavah, and you have the godol hador. Baruch shezachinu.