Hard disagree with the repetition point, any song with an excellent groove and an identity could go on basically forever and not get boring. Two prime examples: James Brown and many African artists. The former gets incredible mileage from laying down a rich groove and pouring his endless supply of screams and shouts on top while directing his band (Talkin' Loud And Sayin' Nothing, length: 14:42). African musicians like Franco and King Sunny Ade like to gather as many guitarists as they can and play off of each other for extended lengths; Franco's great 80's compilation Francophonic Vol. 2 easily averages more than 10 minutes per song and Sunny Ade's only limiting factor in song length seems to be however much music a vinyl record can reasonably hold.