If you’re tired of sitting through ads before movies, you aren’t alone. Earlier this year, the National Association of Theater Owners ruled that trailers should no longer exceed two minutes—that’s 30 seconds shorter than the previous norm—and requested theaters stop playing previews more than four months in advance of a film's release. According to The Hollywood Reporter, theater owners were fed up with criticisms from audiences saying that previews had become too long and revealing. Every theater has its whiners, but the new guidelines confirmed a popular consensus: Trailers feel too long.

Are they longer than they used to be, though? For the most part, probably not. The duration of trailers (as a block, not individually) fluctuates according to the theater chain, the movie, the projected audience, and the time of day. During research for his book Coming Soon: Film Trailers and the Selling of Hollywood Technology, Keith M. Johnston, a senior lecturer in film and television at the University of East Anglia, took note of the length and number of trailers in theaters since the 1920s. What he found was that today’s average trailer sequence—10-15 minutes overall—isn’t so much longer than the run time for previews of the past century.

The typical individual trailer hasn't expanded in duration, either. Today’s two-minute ad is about long as its predecessors in the ’40s and ’60s; it’s on the short side compared to the three-minute average of the ’90s and the four- to five-minute blockbuster model of the ’50s and ’60s. The average number of these trailers played has fluctuated over cinema history, but overall the norm is four to five. While today’s biggest chains can run as many as six to eight—from my own unscientific survey in Washington, D.C., AMC Theaters does this on a regular basis, Regal Cinemas at peak times and for blockbuster movies—many smaller organizations opt to limit the number they show, as is the case at Alamo Drafthouse and Bow Tie Cinemas (four and five, respectively).

So why does it seem like there’s more film advertising than there used to be? Johnston points to a cultural shift in moviegoing. In the 1940s viewers attended the theaters every day or every few days: “It was as natural as checking the Internet or checking a program on television.” Between the typical program's two features were a hodgepodge of newsreels, cartoons, and trailers, generally three to four at a time. So trailers were part of what you were paying to see, one component of the amusing mix.

In the 1950s, movie-ticket sales dropped as television gained ground and former urbanites moved to the suburbs. To lure them back, the previews boasted about new stars, new technologies (such as Cinerama, Vistavision, stereophonic sound), and color. By the 1960s arthouse and self-producers made ever-longer, ever-more-idiosyncratic trailers (for example: Alfred Hitchcock’s ambling, self-produced tour around a Universal Studios soundstage in 1960 to sell Psycho). Though these longer trailers were prone to overexplanation, they were an essential part of the spectacle of going out to the cinema.

Still from Alfred Hitchcock's trailer for North by Northwest (Hydrargyrum/Wikimedia Commons)

“You tended to go for an evening to see all of the range of stuff given to you,” Johnston says. “You were paying for the night so you might as well see all of it.”

The origins of trailer fatigue can be sourced back to the 1970s, when theaters began to show single films for longer periods  (this was a transitional era of “art cinema” and Roadshow movies but also Jaws, the first summer blockbuster) and cut down on advertising so as to spotlight the movies itself. By the time multiplexes arrived in the 1980s and trailers proliferated to fill the advertising demand across all their screens, moviegoers had become attached to the one-big-show model. The 15 minutes of previews stopped being perceived as free extra entertainment. It started becoming a nuisance.

But that’s the long view: What about for those of us who grew up in the modern trailer era? Perhaps it’s the current style of the ads—overstuffed, insanely fast, generally incomprehensible—that is so universally trying. In the 1940s and ’50s, previews tried to persuade the viewer of the movie’s superlative qualities with caps-locked placards and narration (“A mad adventure fraught with bold intrigue!” “The most exciting movie ever screened!” “The most memorable event in the annals of the motion pictures!”). Today they’re still hyperselling, just showing, not telling: Trailers are faster, contain less narration and more explosions, give away key scenes, and contain frames shot in production just for the trailer. Visually, they’re a sequence of show-offs. Viscerally, they are exhausting.

Still of the Transformers (2007) trailer (Youtube)

Of course, there’s a method behind the madness. Studies show the wearisome rapid-fire of striking shots can be effective. It can also turn viewers way off from becoming emotionally invested. In 2013 an Innerscope Research study using neuroscience to gauge the effect brain feedback has on box-office receipts found viewership was highest when audiences engaged emotionally. Trailers should grab the audience early; they should also hold back on “pivotal moments” and special effects, which pull them out of the moment. Sparing audiences of spoilers is important, too. Johnston’s own study of The Hobbit: The Desolation of Smaug trailer this year found over 80 percent reported feeling disappointed with the movie after seeing the trailer, which was jam-packed with "money shots" of Middle Earth.

But maybe the trailers aren’t entirely to blame. Pre-trailer ads, the branded entertainment that plays before the scheduled movie time, are on the rise even if the previews aren’t. Perhaps best known by their monikers—“FirstLook” at Regal Cinemas, “The Countdown” at AMC—these before-showtime spots became standard in 2005 and have been bleeding into the coming attractions ever since. They’re longer than the trailers (20 minutes for most theaters), and are almost entirely focused on entertainment content: 15 minutes are devoted to infomercials and promos for movies, television, and occasionally video games at Screenvision, the single largest company producing them. Their non-entertainment ads are really the only component of in-theater advertising that is actually getting longer, yet they can still be confusingly similar to the trailer sequence.

“Most audiences are not really aware of the distinction,” Paul Rayton, a projectionist for 50 years, told me of these pre-show promotions. “The overall gestalt of a case like that would be that someone might certainly feel that they are being subjected to far more ‘trailers.’”

Theaters hold that viewer comfort is still their primary priority. (Believe it or not, this has been in question ever since they started getting regularly paid to run trailers). It’s the reason for the 10-15 minute average, which Alamo Drafthouse CEO Tim League tells me is a sweet spot according to semi-regular surveys he conducts of his viewers (12 minutes is his target number). But there are also some outside factors that can’t be managed by theaters themselves. Such as the fact that advertisements for the same movies in theaters are also playing on television and in multiple trailers—teaser, international, #1, #2, #3!—often online first. By the time we settle into our seats and are bathed in the green glow of the first MPAA placard, we may already know the “emotional journey.” We may tire of seeing the 50 Shades of Grey trailer for the 10th time. We may be eating popcorn and thus, studies have shown, be immune to trailers' charms.

Today’s best trailers are designed to wake us up, wherever we’re watching. The Star Wars: The Force Awakens teaser, the single biggest trailer success story of 2014, pulled this off by slowing things down. Consider its construction: The spot begins by lulling the viewer into a momentary stillness with a lingering, 20-second shot of a desert planet (Tattoine?), a pause that is broken by John Boyega’s sudden, frantic-looking appearance in the frame, a delightful and much-discussed surprise.

“There has been an awakening. Have you felt it?” a voiceover intones. Over the course of the trailer, we certainly do feel, as choice shots of Star Wars trademarks with makeovers—a robot that looks like R2D2, a strange and illogically designed lightsaber—are interspersed with several-second cuts to black. In a final, rousing moment the camera follows the Millennium Falcon through a hailstorm of lasers. It’s a teaser, not a trailer, per se. But as a 1:30 montage of singular, stirring, drawn-out moments, it’s a masterclass in how to make the most of a short time without cramming too much content in. And guess what? It showed in theaters first.