'Attention span' is given as a reason regularly for not singing long songs - I have to say I don't understand the argument.
Given that I can watch a film or a play of, say 2/3 hours duration, or can read a book for hours on end (given the chance!), why should I not be able to listen to a song of ten minutes (max) without losing concentration.
Providing the film, play, book, song, have been made and executed sufficiently well, and given that they fall within my interest and understanding, why should I need to set a time limit on them?
Veering slightly off-subject, during the making of the Radio Ballad 'Song of a Road', producer Charles Parker played sections of actuality which had been recorded for the programme, to pupils in schools in Birmingham and measured the length they continued to listen to the various speakers. He found that the duration varied between, say a 'well-spoken' highly educated (planner - architect - manager - whatever) and a bulldozer driver, navvy, manual labourer, in the ratio of around four to one, in favour of the manual workers, even when the regional accent was unfamiliar.
This was just an observation on Charles' part; he never went into details, so I don't know how valid his findings were.
Jim Carroll