When Rav Shach turned 100, he told his students that he was going to accept upon himself a new resolution. The students were curious: What new practice is Rav Shach going to adopt at age 100? He told them: “I am going to be careful to always bentch (recite the blessing after meals) from a bentcher [=book].
I find this a little hard to believe. (No litotes intended. I'm not saying it's impossible — just that it's somewhat hard to believe.) After all, Mishna B'rura (185:1) says "one who is particular will take care to bless, l'chat'chila, from a book and not by heart", so I'd imagine this is something Rabbi Shach may well have been careful about already by the time he hit age one hundred. So I'm seeking a better source than Rabbi Rosner's say-so. Anyone have one?