In a commentary published in this journal in 2010, I wrote that it might be reasonable to suggest that it takes 10 000 hours to complete a PhD. I have had a generally positive response to this suggestion and my colleagues and I have started to incorporate this concept into some of our student planning processes. One of the issues that have arisen as a follow-up to 'How long does it take to get a PhD?' is 'How much time should a supervisor devote to the supervision of a PhD student?' Of course, similar questions can be asked regarding the supervision of students registered for other degrees, but it is appropriate to focus on the doctorate, as it is the universally accepted qualification required for a research career.