When engines are m-ued, whether they are shut down or running, the rear headlight's electricity comes from the controlling unit. There is a limit to the number of locomotives it can pass through and still be relied on to illuminate the headlight.
This consist is long enough that it would be prudent to have the rear unit at least idling and its own rear-facing headlight switch turned to DIM, if that is going to be the marker. The preferred method of addressing this type of movement is to set up the rear trailing locomotive as a Distributed Power remote unit. An end-of-train device could be used, but why take one away from where it is really useful, when you have a built-in marker viz the headlight.