I agree with what is being said. Most pop songs and country have a 3.00min standard although it is not carved n stone.

Most rock songs are usually a tad longer allowing for the traditional long intro and solos etc.

That said a song can be any length as long as instrumentally or storywise it is captivating and not boring. Most pop or country songs should have as a benchmark a max of three verses and three choruses regardless of what order the appear.

(PS Much as I like American pie the full blown version does get tedious and boring and most people I know who perform it trim off a considerable bit)

http://www.soundclick.com/bands/songInfo.cfm?bandID=687727&songID=5238055