I was MCing a concert at Whitby a couple of years ago and everyone had been allocated 20 mins, and I'd built into my running list a bit extra time for getting on/off etc. A certain Irish storyteller did 35mins (one story) and would have continued for longer if I had not managed to get him to come off stage ("Well now - to cut a long story short...."). Later in the week Bob Davenport is MCinc a concert - everyone has 10 mins (bad programming - far too many artists) SAME story teller is into about 18mins when Bob just walked on stage - said "thank you that's all - and our next singer is....."
It has happened to me too, with previous acts over-running, sometimes by 15mins - it's not fair on the other performers as it cuts down the time they have available to play, or the concert overuns dreadfully.
When the late Vic (Prof.Wingnut) and I were doing concerts/clubs/ whatever we knew exactly how long each item took - including getting on and off and applause (if there was any!)It ain't difficult to make a note of how long each song/tune/etc in you act takes, and if an MC want s 20mins spot you should be able to give them exactly 20mins - you have to do it on radio or TV.
Dave Sunshine