I try never to repeat the same songs at the same locations, unless they are really good songs which go down well. I will repeat them on a couple or three month cycle, when I forget when I did a song last. If I ever get a request, I will let you know if I still remembered the song. If the same people go to other places where I sing the same song, then it is their fault, not mine. Most people I know reguritate quite a bit anyhow. We also tend to practise in the car on the way to places. Just keep doing whatever you can. JohnB