You see the same act twice at a festival. Maybe there's nothing else on, or you saw them the first time because you didn't want to miss, them then you realise that they are on in another concert before another act you don't want to miss.
How much repeated material do you find is too much?

And I'd be interested to know how often performers change their music and their patter (I think I find the repeated jokes harder to take than the music).

I can understand that young musicians may not have enough material worked up to performance standard, for several different performances and anyway want to finish on the best bit.