Most interesting, I thought, was his comment about this earlier routine compared to the present: "So I was very disciplined about it," he says, then quickly concedes he doesn't have such discipline now: "I don't have to."
It's not clear from what's cited whether he doesn't "have to" because of his success as a writer or because he has more time to devote to writing (or both). Either way, it got me thinking about the compression of time, which Trollope also used (writing with his watch in front of him), and how useful that is for producing forward momentum.
It appears possible to be most productive as a writer when one feels least able find a spare moment to write.
So there really is no excuse not to write that book that's been kicking around in your head for years, which you haven't gotten around to writing because of your day job, or because you're "so busy."
Right?