The hook is usually something that swells up at a moment you can point to, but sometimes it’s more structural and surrounding: something is getting to you in a song and you come to see that it’s an unusual large-scale design. For example, the refrain in “Walk Away Renée” by The Left Banke always arrives too big and soon, like a tidal wave, because the verse seems like it’s going to go a normal sixteen bars but only goes eight.
At the other end of the segment-length hook spectrum, Pink Floyd’s “Comfortably Numb” has a refrain that lasts nineteen measures—more than a minute—way, way beyond the eight-bar norm for pop choruses. The length is partly disguised by a verselike quality, including some variation of words in its second occurrence; it shuttles back and forth between four-bar sections based on the chord changes of D-A and C-G, each section stately in itself because it repeats a 2-bar statement.
As a result, when you get to “I have become comfortably numb” in measures 17-19, you feel as though you’ve gone through a long climbing tunnel and now you’ve come out in a bright and different place.
See Andrew Goodwin’s ambitious structural analysis in the post just below on “Whole Lotta Love.”
Also see my reluctant note on Madonna.
2/8/17 Here’s another good one: in Jump, Little Children’s “Say Goodnight” (1998), the chorus, once it clearly gets started at 0:57 and 2:07 after a transitional section, takes ten measures to arrive at its gloriously repeatable peak, where you find out what the chorus is.
 For comparison, notice what a strong (and nicely appropriate) feeling of endlessness Aimee Mann gets by prolonging the “It’s not going to stop” chorus of “Wise Up” just four bars beyond the normal eight.
 There’s a remarkable structural hook in Madonna’s “Like A Prayer.” In roughly the first half of the song, up till 2:20, there are 61 measures of 4/4 time, of which the huge majority, 45, have no beats. That’s right, the ratio of beatless measures to measures with dance beats is 45 to 16. Pretty spiritual, huh? (After 2:20 there are 90 measures to dance to.)