Just FYI, copy editors don't work directly on the final documents, that's what layout people do. Editors hand off explicit instructions to the layout people like, "On page X, section 'Stuff Matters,' replace the second paragraph, third sentence to the end, 'Ipsum lorem ...' with 'The quick brown fox jumped.'" The layout people then make the changes, fitting it in with minimal impact on the surrounding text, correcting page references and such as necessary. There's a lot more process to publishing than most fans realize, and everyone involved has multiple projects with schedules to meet. When JH says it's hard to fit things into the schedule, that doesn't mean he could fix things by staying late on a Thursday. He's not the only person who needs to work on it. And because of the difficulty of organizing things, and the cost of re-printing, they usually collect errata into batches, synced up with times that they'd be re-printing anyway.