Hi Jeanne and Scott,
Congratulations on the release of your new book, I remember taking the OCP 8 book out from the library at university. I had it for the entire year but I didn't consider working towards certification.
At a rough estimate, how many hours a day/week would you recommend on preparing for certification after having had a break from coding?
It depends on your level of knowledge and whether you've taken a cert exam before. For example, people who are Java 7/8 certified generally have an easier time preparing for a Java 11 cert, in part because they already know a lot of the kinds of questions the exam asks. As a guess.... if it's your first time it can take 2-3 months of studying for an hour a day. I would try to do a chapter a week (if possible). Some chapters will obviously be easier than others, but it will at least help you learn your own pace to get a better estimate in the future.