To put it from a performer's point of view, I don't think we've ever done the same set twice anywhere, and certainly not at one festival. But it does seem that some performers seem to have 'current' sets, usually from their latest CD. Personally, I'd get very bored with that, and I think that would show in performance.

As to the introductions, I think it's not unreasonable to use a similar introduction each time one sings a particular song - and yes, that does sometimes include - not necessarily a joke - but something which makes people smile or even laugh. But the introductions are intentionally to put a song in context or to be informative, so some repetition is inevitable. And when you have an introduction to a song that works well, you (or at least, we) tend to stick to it, more or less.

I would have thought that the content of the set is more important than whether someone has heard a similar introduction at another event.

Barbara