3 minutes. Verse, chorus, verse, chorus, bridge, chorus.
A band called the Minutemen, who are known for playing the theme of Jackass, had most of their albums last 18 minutes long, and consisted of 18 songs each, ironically. And several great stoner and metal bands have songs that last over 10 minutes.
It doesn’t matter how long a song is, as long as you can keep it interesting.