"How do you deal with a singer who sings the same old two or three songs over and over again"
Part of the assistance is passing on new songs - London Singers Workshop amassed a huge 'dip-in' archive made up originally of songs to learn, but which later broadened into Irish, Scots, American and International sections and included lectures and radio programmes for those who wanted to 'lift the corner to see what was underneath.
Like Topsy, thanks to the efforts of those who wished to help, it "just growed".
MacColl and Seeger had a large file of songs in duplicate, traditional and their own, for sending out on request.
One of the features of the Singers Club was 'The New City Songster' 20 volumes of contemporary songs edited by Peggy Seeger and contributed from songwriters from all over the world.   
Having said which, deep-sea fisherman Sam Larner sang 'Butter and Cheese and All' once a week throughout his long life at the singaround at his local pub, The Fisherman's Return, in Winterton, Norfolk - some are good enough to get away with it, some aren't!
Jim Carroll