when does a song become to long

when they just keep playing the same thing over and over. for example, The Beatles' "Hey Jude" and Derek and the Dominoes' "Layla"
However, a song can be long as hell and still be awesome, For example Dream Theater's "A Mind Beside Itself" is almost 20 minutes long.

don't care as long as the song is good, it mainly does depend on the song

a song becomes too long when it begins to suck

i've got songs i like that are over 20 mins.

i've got songs i think are too long after 0.5 seconds.

it could be within 2 seconds if i hate that song.

Uh Sonatas and Concertos are sometimes 1hr+, when all three or four movements are played.