I got myself the Harry Potter 3 movies box (I could pretend it's for my kid... ;-) ), and when I was watching the first movie, which is quite long for a movie, well over 2 hours 1/4, I noticed how early the movie was over, compared to the playing time mentioned on the box: the 138th minute, vs. 147 minutes of playing time. So I kept watching the credits...
The box wasn't actually lying, just exaggerating a bit, total playing time is 146 minutes and a few seconds. There's a whole 8 minutes of nothing but scrolling credits, which seems rather excessive to me. 8 minutes, that's between 5 and 6% of the total playing time, of what is, like I said, a really long movie. Wow.