Even more to the point , have an MC with sufficient strength of character to 'hook' an act as soon as they start to overrun .

I wrote here a while ago about the Dylan Night From Hell, featuring among other things an act that did Percy's Song at a nice steady andante (16 verses) and the guy who did I want you & took the first verse at speaking pace to show off the lyrics... then took the rest of the song at the same pace. Both excellent performances, but they really needed an evening of nice brisk songs to set them off. As the evening wore on, the MC actually asked people to do shorter songs, or cut a few verses out of the longer ones if necessary - "so no Sad Eyed Lady of the Lowlands, no Desolation Row with all the verses, all right?". Two acts later and what did we hear...

They're selling postcards of the hanging
They're painting the passports brown

Every bloody line of every interminable verse of Desolation Pigging Row, taken at the authentic funereal trudge. (I'm a big fan of Dylan generally, but I've never much liked that song.) Unfortunately the MC let the blighter get on with it. There was never a better case for a gong, or a strategically-placed round of applause (I've seen somebody being clapped off stage in mid-song, although in that case it was accidental).

(I did Hard Rain the year before. Three minutes flat. Stormed it.)