Maybe a better question would be, how few verses. Most two-verse songs feel incomplete to me. A song needs at least three or four verses to feel right.

I do think that when writing songs four or five verses is a pretty good goal. It takes that much to develop an idea in a song. Longer songs do tend to lose attention.

But story songs are a different ballgame. Still, it helps to be succinct but still convey the story completely.

I have sung under church choir directors who tailor songs to fit a certain time in the liturgy, and then they quit singing - I've even had some quit mid-verse. Kinda like coitus interruptus, church-style. In some songs, you really need to sing all the verses. Don't stop "We Three Kings" before you get to the myrrh. If you're singing a Trinity song, don't stop at the Son. If you're singing a murder ballad, don't stop before the victim dies....

-Joe-