My latest at Adfreak examines the ways in which those post-credits stingers have become an integral part of the movie marketing cycle, especially for franchise films:

In the last week, a rumor that had been bouncing around the internet was confirmed when director James Gunn revealed that, yes, Guardians of the Galaxy Vol. 2 would have an epic five post-credits scenes. For those of us who feel like most movies could easily lop off 20 minutes or so without losing anything meaningful from the story, it means we’re going to have to wait even longer to OMG get out of the way I need to go to the bathroom.

The number of post-credits sequences has steadily increased since Marvel Studios revitalized the concept with 2008’s Iron Man. That scene featured Samuel L. Jackson as Nick Fury emerging from the shadows of Tony Stark’s living room and introducing him—and the audience—to the reality that a wider world of superheroes existed, ultimately setting the stage for The Avengers four years later.

Source: Stay for the Credits: How Bonus Scenes Became a Crucial Part of Movie Marketing