It depends entirely on the venue and audience response. For a senior home performance, I'll usually want to provide variety and several selections. Since there'll be some kibitzing and time restrictions, I'm guessing the average song length might be 2 - 2 1/2 minutes.

However for a dance, that all changes. Average song length will be longer, maybe 3-5 minutes... even longer if you're doing a medley for something like a 'robers dance'

Most important, you have to always 'rread' your audience... be prepared to shorten of lengthen a song depending on how people are responding. You might be playing a song with only a few dancers oon the floor and after 3 minutes, you're ready to end... then some more couples come on the floor. You have to either extend the song or go into something similar with no more than a few seconds 'dead air' time.

This is where (the flexibility) arranger mode has it all over MIDI or Mp3.

BTW, another option is LIVE! 4 mode... but that's a whole 'nother subject.