Guest, your statement that "Peace, a good songwriter gets the song in an hour, polishes it in an hour and it's done. No song should take 120 hours!" sound a bit tautological. I.e., it sounds like you'd dismiss the writer as "a bad songwriter" just for taking so long to work on a song, no matter what the finished product was.

With Paul McCartney in the news now for turning 64, let me remind you that "Yesterday," which many consider one of his finest, if not the finest, BEGAN as a melody that popped into his head -- he hummed it to his mates and asked them what the name of it was! -- then went through a phase where its lyrics were "Scrambled eggs, Oh, my baby, how I love your legs! ..." and later was given the lyrics we now know.   
So much for your "an hour and it's done" rule.

I've also seen some of Woody Guthrie's original yellow-pad notebooks where he pencilled in early drafts of songs like "Deportee," "Pretty Boy Floyd," and others. Sometimes the notebooks show several different versions/incarnations of a song. In any case, Woody customarily worked and re-worked his lyrics over some period of time. And usually the songs were better for that.

BTW, when I speak of "working on a song for hours," that may mean playing and singing the song a number of times while entertainining new lyric possibilities or tune modifications. It doesn't necessarily involve a thesaurus and rhyming dictionary or breaking out the music theory texts.   Sometimes the muse makes brief visits to you now and then over a period of hours, days, or longer.