The Yated on parshas Noach has an interesting vignette in the article on Rav Shimon Shkop ZT”L, a maggid shiur in many yeshivas ( including Telz, Grodna, and YU). Some talmidim spent time talking to him in learning. They apologized for taking so much of his time. He responded that just like maaser is a segula for being rich, giving of one’s time to be melamed is a segula for acquiring knowledge. By giving, one gains.
I also heard from a rebbe of mine that Rav Shenur Kotler ZT”L, when he was very sick, made a mecha’ah against those claimed his father was against being Marbitz Torah. In other words, Rav Aharon Kotler ZT”L did NOT change his mesorah of being Marbitz Torah and helping the klal. Only later talmidim “shelo shimshu kol tzarcheihem” claimed such a thing.