Four hours, narrated by Luke Oldham, is a sensible shape for instruction of this kind. Long enough to cover the ground properly, short enough that a listener could get through the whole thing before the equipment even arrives.
No listener scores have been posted yet, so there is nothing to report on that front. Approach it as a working guide rather than an evening’s entertainment: the sort of title you play once with the handset in front of you, then return to when something specific needs checking. Anyone assembling a household emergency plan, or heading somewhere without reliable signal, is the intended audience. What is currently available is set out below.