Another thought on the "intro" question would be that intros would also vary according to the reason for the gig.

Case in point, would be educational shows of varying nature. I've been to a couple public performances by various shantymen where the intros wound on for most of the set, and the show was greatly enhanced by it. They gave the shanteys the background that was needed for the avertage layman to really understand why it was the way it was.

So for me, at least, in those cases I can see introductions as being entirely necessary, and at times almost being more important than the songs they introduce (imagine singing a Stephen Foster set without the proper background...)

M