The OP is obviously not familiar with traditional song of any kind. If he was he would know that the vast majority of folksongs are narrative songs and that they had been honed down by discerning singers (and audiences) for several centuries. To suggest that they then might contain extraneous material is ridiculous. Recently written songs, perhaps.

I have been singing folk songs for nearly 70 years and I would say the average length would be 7 or 8 stanzas but some much longer, and I have never had anyone even hint that a song was too long. Yes, I have heard people sing a long ballad in an inappropriate situation but that is all about reading an audience.