"I can do this all day," Captain America (Chris Evans) famously declares in multiple Marvel movies, usually when he's being beaten to a pulp.

But can Marvel fans sit and watch him all day, with no intermission or bathroom break? That's a different question.

Marvel's ensemble movies have, slowly but surely, been getting longer, and Avengers: Endgame, which hits theaters April 26, has been rumored for months to be pushing three hours. Now the run time's official: 3 hours and 58 seconds, according to CNET sister site ComicBook.com, which spoke to director Joe Russo at the annual CinemaCon event in Las Vegas.

Earlier reports had the film running slightly longer, 3 hours and 2 minutes, to be exact, according to a run time posted by AMC theaters on March 25 and then later deleted. "We just sped up the credits is what we did," Joe Russo told ComicBook.com.

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The length doesn't seem to bother Marvel fans who've been lucky enough to grab a sneak peek. But apparently no one needed to escape for a sneak pee.

"We have screened the movie four times for audiences now," the other Russo brother, Anthony, told Collider in February. "For the first three screenings, not a single person got up to go to the bathroom."

In an interview with Collider published in early March, Marvel Studios President Kevin Feige made it clear the movie would get the "exact right running time."

"We don't look at run times in terms of mandates or anything like that," Feige said. "Every movie should feel like it's an hour and 45 minutes. Now, some movies can be 90 minutes and feel like they're four hours. And some movies can be three and a half hours and feel like 90 minutes ... And every version of Endgame thus far, and the ones that we're honing in on, feel very good."

Bathroom-break app

Still, a three-hour film is a first for Marvel and might require a bio break even for those who absolutely hate the thought of missing any dialogue. Few people know more about movie bathroom breaks than Dan Gardner, co-creator of RunPee, a mobile app that recommends the best times to get up and answer nature's call during a movie.

Gardner used RunPee data to compare the lengths of all MCU movies dating back to the first film in Phase 1, 2008's Iron Man. (That film's 2 hour and 6 minute run time seems as quaint as Cap's dating skills compared with the Endgame three-hour time.)

"The trend is definitely toward longer (MCU) movies, but that is an inevitable consequence of the stories involving more and more characters," Gardner said. "The first Avengers movie was considerably longer than any of the first five MCU movies because it involved all of the characters interacting and forming a team."

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The shortest MCU film of all is 2008's The Incredible Hulk, at 112 minutes. Thor, from 2011, is just 114 minutes. Doctor Strange, from 2016, is 115 minutes. And 2015's Ant-Man ran 117 minutes.

See the pattern? Those films all focused in on one main standalone character rather than needing to weave together multiple heroes and their stories. But they, too, seem to be getting longer: Captain Marvel, the newest MCU solo film, runs 132 minutes.

Now playing: Watch this: Avengers: Endgame trailer takes you back to the start

Avengers: Endgame will be the longest MCU film if the Russos keep it at the 180-minute mark. Next longest is the 2018 film that sets up Endgame, Avengers: Infinity War, coming in at 149 minutes. Captain America: Civil War, from 2016, comes in at 147 minutes, with 2012's The Avengers at 142 minutes, and 2015's Avengers: Age of Ultron at 141 minutes.

"If you break it down by standalone versus ensemble, then the average run time of a standalone is 123 minutes and the ensembles are 139 minutes -- not including Endgame," Gardner notes. If Endgame sticks to three hours exactly, Marvel's ensemble films' average run time is 144 minutes.

The run times aren't really surprising, says Robert K. Elder, who calls himself a "recovering" film critic and has written 11 books, including The Film That Changed My Life and The Best Film You've Never Seen.

"When you have this many characters -- including a space pirate raccoon and a Norse god -- this kind of length is inevitable," Elder told me. "Marvel is doing something unprecedented in creating a cohesive cinematic universe. That means there are a lot of character arcs and loose ends to tie up."

Wait for the battle build-up scenes

If you do need to take a quick break, whether a restroom stop or concession load-up, Gardner offers a tip.

"In action movies there is usually a scene or two preceding the final battle, where the action slows down a bit and gives the audience a chance to wind down a little," Gardner says. "A good example is in Zero Dark Thirty, (where) there was a very long chopper ride scene as the team headed for Osama Bin Laden's compound."

How do you know when the battle scene is looming? Gardner notes that RunPee will have spoiler-free Avengers: Endgame "peetimes" added to the app by the film's opening night.

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Of course, the simplest tips of all are obvious, especially if you don't like missing anything. Resist the lure of that gallon-sized Icee. Or at least sit on the aisle for a quick exit if needed.

"I'm a seasoned moviegoer, so I always have a game plan," Elder says. "I eat beforehand and make sure that my bladder is empty. Lock and load."

But just because Avengers: Endgame is promising to test fans' ability to stay put, doesn't mean movies as a whole are trending longer.

Now playing: Watch this: Avengers: Endgame's heroes are picking up the pieces

"Long movies are expensive, so they are relatively rare," Elder said. "The height of this era was the early-to-mid 1960s, so it's a fallacy to think that (today's) movies are longer."

Those intermission rumors

Some of those classic long 1960s films came with intermissions. During a cinematic intermission, the movie action stops, usually with a still image announcing the break frozen on the screen. Early movie technology required the intermission so projectionists could change reels.

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On Feb. 5, movie writer Alan Cerny, co-host of the Matinee Heroes podcast, suggested in a tweet that Marvel might be considering an Avengers: Endgame intermission. Cerny later said the report was based on "fan discussion and (online) speculations," and he doubted it would happen. But in response, several fans pointed out that intermissions are standard during movies shown in India.

Gardner of RunPee is no fan of intermissions.

"I think an intermission is pretty disruptive to the experience," he said. "The break would have to be at least 15 minutes long to be of any use. I think it just creates a mess."

Even though the data shows that Marvel's ensemble movies are slowly lengthening, Elder views a three-hour Avengers: Endgame as a one-time necessity, not a trend.

"Marvel movies will go back to being 120-minute-and-below popcorn experiences," Elder says. "(Avengers: Endgame) is the Lawrence of Arabia of comic-book movies."

But he thinks that if Marvel builds it, moviegoers will come.

"If Kevin Feige and the Russo Brothers say they need three hours, they've built up a lot of goodwill (and) audiences will go with them," Elder says.

So just be like Captain America, and plan to stay put for a while.

Originally published March 6.

Update, March 14: Adds link to new trailer

Update, March 25: Adds AMC deleted run time.

Update, April 4: Adds Joe Russo confirmation of run time.