It is known that Rav Elyashiv answered she’eilah after she’eilah, one by one, without even looking anything up in a sefer. Everything was literally at his fingertips.
Rav Bentzion Kook once asked the Rav, “How is it possible to remember the entire Torah? Does it depend on chazrah, on how many times one reviews?”
Rav Elyashiv answered, “That too.” Rav Kook asked, “And what else?”
Rav Elyashiv added, “The Torah has an additional name. That name is Uf, which means to fly away.” Rav Elyahsiv then quoted a gemara in Maseches Berachos that says, “Gloss over it with your eye and it will have disappeared.”
One shouldn’t take his eyes off the Torah because if he does, the Torah will fly away from him. Rav Kook then asked, “What amount of time is considered hesech hada’as, taking one’s mind off the Torah? Rav Elyashiv blinked his eyes and said “That is already a diversion, hesech hada’as.”
One cannot take his mind off Torah for even a minute. The way to achieve that is by valuing time, not letting a blink of an eye go by. ~ The Gadol HaDor