With some reading, I see that the WD Utilities includes the ability to set the sleep time for these units.
Is that parameter set on the My Book, or on the host computer? Asking because my intention is to connect it to the USB port of my router to use as a network drive. In this case, will it spin down after x-minutes? And will it remain visible on the network in this state? And will it wake up when, for example, selected in Windows Explorer? In other words, is it going to remain at all times accessible, but spin down when not in actual use?