I think Richard is right that the repetition of the first verse at the end of a song is becoming more common practice; I've noticed it a few times, but I haven't paid much attention to notice whether it happens with specific songs, or types of songs, or in specific occasions. I'd regard it as simply a sort of framing technique on the part of the singer to say, in effect, that the story is now over.

My impression is that the repeated verse is sung at a different pace when used to conclude the song - otherwise you get the alarming sensation that the singer is going to sing the whole thing again!

I wonder whether the practice is more common in singarounds, than say in recordings or concert performances, since it acts as a useful signal that the singer is finishing their turn and it is time for the next person.

I can't say that I've found it irritating or time-wasting generally; perhaps in some cases it might be meant to illustrate the cyclical nature of time - "in my end is my beginning", but I think it really is just another way of saying "That's All Folks!"

Matthew