This past weekend saw the opening of Guardians of the Galaxy, which has been touted as a very different kind of summer blockbuster. And while, yes, it leans harder on comedy and quirkiness than the average superhero movie, it stands out for another reason: At 121 minutes, it’s downright short compared to most of the movies you’ve been sitting through for the past four months.

In fact, 2014 might go down as one of the most butt-numbing years in summer-movie history. That’s thanks, in part, to Marvel, the company that gave us such super-sized superhero movies as Captain America: The Winter Soldier (136 minutes), The Amazing Spider-Man 2 (142 minutes) and X-Men: Days of Future Past (131 minutes). But epic length is hardly relegated to just superhero fare; it’s becoming a hallmark of all blockbusters. Dawn of the Planet of the Apes is 130 minutes (having evolved 25 minutes longer than 2011’s Rise of the Planet of the Apes). And Transformers: Age of Extinction clocked in at an endurance-testing 165 minutes, a length bemoaned by film critics on Rotten Tomatoes and moviegoers on Twitter. (Not that that kept anyone away; ticket sales for the fourth installment in this toy-based franchise just surpassed $1 billion.)

Considering the last few years of non-stop Bayhem, marauding Pirates, and super-hero tentpoles, we should probably have grown accustomed to overlong run times by now. Yet bemoaning blockbuster lengths remains a favorite pastime for those who cover movies. “This cinematic bloating is totally unnecessary,” wrote Jim Slotek of the Toronto Sun recently. “It’s one of the paradoxes of our age. As attention spans get shorter – movies get longer.”

Some of our biggest summer franchises are microcosms for this runtime escalation: Transformers, Batman, Spider-Man and Pirates of the Caribbean entries have mostly gotten longer and longer throughout their multi-installment releases. (Though in its fourth go-round, Pirates was pared down to a mere two hours and seventeen minutes.)

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“Speaking as a fan, I don’t understand it,” says Tim League, CEO of the film-fanatic-friendly Alamo Drafthouse movie chain. “To me, over-bloated runtimes suggest there are not enough brave souls surrounding creators to tell them the hard truth — you need to slash and burn; you need to have a concise story. While there is much to enjoy in these blockbuster films, many would benefit from a tighter focus with less characters and subplots.” However, Phil Contrino, chief analyst at BoxOffice.com, doesn’t believe moviegoers mind the extended runtimes, and that they create more of a “more bang for your buck” scenario. “In the eyes of fans, more really is better when it comes to these films,” he said. “The paying public clearly wants as much for their money as they can get, so the prolonged length of key tentpoles is not yet an issue.”

But are summer blockbusters actually getting longer, or is there a “in my day, movies were shorter and better and they cost a nickel!” effect going on, where they just seem longer? To find out, we got out our stopwatches and graph paper and looked at the last 30 years of summer releases.

First, let’s look at the average runtime of the top ten highest-grossing movies each summer. These were purely picked by gross, so they are a mix of all genres, not just your traditional blockbusters.

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Summer runtimes were relatively low in the early ’80s, but that was before “summer blockbuster season” became a cultural touchstone. The average runtime first surpassed the two-hour mark in 1992, but Hollywood put out a more diverse mix of films back then: That summer combined popcorn fare (Batman Returns, Lethal Weapon 3) with dramas like Unforgiven and Far and Away. Average times would hover around the two-hour mark for most of the next decade. There were occasional spikes, like 1998’s summer of destruction, which let directors really take their time in destroying cities and planets in movies like Armageddon (151 minutes), Deep Impact (120 minutes) and Godzilla (139 minutes).