Brevity or eternity, how long should a song last? The rule of thumb, by professional songwriters in Nashville, is three minutes. The number three is not set in concrete, but I've heard that number pop up consistently at writing seminars. So why get hung up on a number? No reason to, except that a pro (someone with a track record) is trying to say, "If you go over three minutes, it had better knock a lot of listeners' socks off, or it's doubtful it will break any airwaves beyond a garage studio wall."
The most-recorded song of all time, "Yesterday," by Paul McCartney and John Lennon, is 1:04 minutes long. One of BMI's highest-sales songs is "Gentle On My Mind," 2:56 minutes, written by John Hartford. Then there is the marathon No. 1 hit "Maggie May," 5:46 minutes, by Rod Stewart and M. Quittenton, that launched Stewart's career in the U.S. A good story song can get by with more time on occasion.
Another rarity is a vocal such as Keith Whitley's. He was usually involved in the production of the songs he sang and often went over three minutes. His eleven songs on hisGreatest Hits - Keith Whitley album averaged 3:34 minutes per song. A great song with a great vocal can make a difference, but most songwriter demos are not as good as Keith's vocals. Usually, your best bet is to tighten up your song toward the magic three minutes for brevity and stay on the safe side and then have less worry about the listener tiring of a song that seems too long.