About 17 years ago I was on a flight with a Gadol Bi-Yisrael. I saw him after we landed waiting for his luggage [no entourage - he was flying alone]. To be honest, I was a bit disappointed. I thought that he would have a sefer with him and would be learning while waiting [like in the stories...]. But no sefer. In general, this Gadol wasn't known for having his head in a sefer every available second. Yet, he knew EVERYTHING. Nigleh and Nistar. Bi-Iyun.
I have an explanation: Maran Ha-Rav Hutner once said about a certain Talmid Chochom "He will never become a [true] Talmid Chochom. He is too busy learning."
Profound.
It is not enough to just learn sefarim. One must take time to close the sefer and DIGEST what he learned. To think about it. To analyze. To take ideas further and see in what really interesting places he ends up.
This Gadol was probably doing JUST THAT when I saw him waiting for his luggage. [BTW - This gadol had a close kesher to Rav Hutner... They are probably learning together RIGHT NOW!!]