At the first two clubs at which I was a resident I frequently got the job of starting the night (either because I was reliable or it got me over with quickly - I don't know) but I always though it was disrespectful towards the audience to inflict the same few songs on them week after week. This certainly encouraged me to learn a larger number and wider variety of songs; along with the excitement and satisfaction of presenting new material on a regular basis.
However at one of these clubs a fellow resident performed "The Irish Rover" five weeks in succession; now what was worse, his repetition of the same song so often or me for realising that he had done?