A small personal story. About 5-6 years ago I arranged with his son to see Chacham Ovadia after mincha. After praying, I quickly went upstairs and entered his room about a minute or two after mincha was over.
I was shocked to see him already in his chair, jacket off, glasses pushed up, pen in hand, concentrating deeply while writing the continuation of a long piece that he didn't finish before mincha. His son literally had to raise his voice while standing right in front of his desk to get the Rav's attention. To see someone so deeply entrenched in learning in just a few seconds was truly special to me.