Longer the better. Outside groove without breaks to the center, please. Jethro Tull “Thick as a Brick” comes to mind first.
Good songs, with musical and lyrical content to justify it, then long. Seconding the the Tull example above.
Bad songs or lazy pop music padding out one verse and a chorus, shorter the better.
In my younger days Iron Butterfly’s In-A-Gadda-Da-Vida was a favorite (all 17+ minutes of it).
Doors; The End
Lou Reed’s Metal Machine Music.