Filmmakers and film distributors have long butted heads. Orson Welles’s famously sent a 58-page memo to Universal Studios that detailed every supposed mistake the company had made in altering his final cut of 1958’s “Touch of Evil.” And in the modern era, the DVD “director’s cut” can turn a two-hour epic into a four-hour marathon. The battle lines are drawn: Directors typically want more freedom, and their distributors want to keep things shorter and simpler.

But in recent years an unusual trend has emerged, and this summer has seen its apex: More studios are releasing — still some six months before the high-minded Oscar season — films that are running far longer than what most audiences and critics have come to expect — or enjoy. This weekend, “Pirates of the Caribbean: At World’s End,” the third installment of the blockbuster franchise, will ambush theaters with a running time approaching three hours. A few weeks ago, the 140-minute “Spider-Man 3” broke box office records. And earlier this year, two other highly-anticipated films from big-name directors — David Fincher’s 160-minute “Zodiac” and Robert Rodriguez and Quentin Tarantino’s 191-minute “Grindhouse” — surprised industry watchers not just with their girth but with their tremendous thuds at the box office.

“Grindhouse,” which offered a double-feature for the price of one ticket, became a unique case-study for how audiences view the subject. At one particular 8 p.m. screening in a Times Square theater during the film’s opening weekend, at least 70% of a near-capacity crowd walked out halfway through the movie, shortly after Mr. Rodriguez’s portion had concluded. While some analysts have claimed that audiences were confused and misinformed about “Grindhouse,” not realizing it was a double feature, no doubt a majority of those patrons decided to make an early exit precisely because they knew it was a three-hour event. Given the option, they preferred a 90-minute spectacle.

So why, then, would studios such as Disney release films like the three-hour “Pirates of the Caribbean: At World’s End” when the conventional thinking says most patrons prefer a short escape? Why spend the extra money making a long movie — especially one targeted at children — when you don’t have to?

“Studios are all trying to outdo each other, with the mentality that bigger and better is what audiences want — particularly with these sequels that need to have more action, characters, and storylines to get people out to the theater,” Chad Hartigan, a box office analyst with Exhibitor Relations, said. “I also think studios have reached the point where they are listening to fans more, and hiring these unconventional directors like Sam Raimi [for “Spider-Man”] and Gore Verbinski [for “Pirates of the Caribbean”], and then when their films are successful, the studios are allowing these guys free rein to make sequels that come in at 2:30, 2:45, even three hours.”

While no studio would go on record to discuss the inflated running times of “Pirates,” “Spider-Man,” or “Grindhouse,” surveying the life of the “Spider-Man” movie franchise seems to reinforce Mr. Hartigan’s line of thinking. The first installment, which grossed more than $400 million in 2002, was kept to a taut 121 minutes. The second chapter arrived in theaters just six minutes longer. This year, the third chapter arrived at an inflated 140 minutes.

The “Pirates” trilogy reveals much the same progression, growing from 133 minutes in 2003 to 150 with 2006’s sequel and, finally, to this week’s 168-minute finale. That’s nearly eight hours of adventure.

“This isn’t ‘Rocky 4,’ which felt 75 minutes long and seemed like it was only a training montage and a fight,” Mr. Hartigan said. “It’s come a long way from there, and the theory here is the more crazy stuff in the movie, the better. It’s a very sequel-based thing; studios are less likely to put out a threehour movie if it’s the beginning of the franchise because they don’t want to give audiences anything to complain about. But once audiences have said they like the characters and the story, then it becomes a safer bet.”

None of which is new thinking in Hollywood circles. As far back as “Star Wars,” sequels have tended to clock in longer. But many studios refrained from releasing sequels in the 1970s, ’80s, and ’90s that eclipsed the 140, 150, or even 180-minute mark because a longer running time limited the number of screenings a film could have on a given screen on an average day. Last Friday, as the 89-minute “Shrek the Third” was opening across the country with more than 4,000 prints, the average theater could open at 11 a.m. and squeeze in anywhere between six and nine showings of the film on a single screen per day. But with a 168-minute “Pirates,” that number shrinks to five, or even four showings.

In short, a longer movie traditionally means weaker daily business for the theater, and in turn, less money for the studio. So we return to the question: Why make a three-hour children’s movie?

Patrick Corcoran, a spokesperson for the National Association of Theatre Owners, said the economics of today’s movie industry have changed dramatically over the years. “It’s not the issue today that it was 10 years ago,” Mr. Corcoran said of this year’s trend toward longer running times. “Now so many multiplexes have been built that theaters can devote three or four, or even five screens to a single title and have just as many screenings in a single day. There’s been a steady rise over the last 10 years of more screens per theater. And theater owners would always prefer a longer movie that people love over a shorter movie that no one will come to.”

As Mr. Corcoran notes, the box-office champions of recent years have been longer films. This year’s biggest winner thus far, “Spider-Man 3,” is one of the longest of 2007. Last year’s box-office champ was the second longest of the year, the 150-minute “Pirates of the Caribbean: Dead Man’s Chest”; 2005’s top title was “Star Wars: Episode III – Revenge of the Sith,” which ran 146 minutes. In 2003, “The Lord of the Rings: Return of the King” — a safe sequel if there was one — clocked in at a gargantuan 210 minutes. With numbers like these, studios are not going to stop chasing the popular franchise or releasing the longer sequels any time soon.

But that may have two unexpected consequences. For starters, as these hit sequels get longer and eat up more screens, there will be fewer and fewer screens open for counter-programming, ensuring there is no space available for a competing film to open (this week, the only film opening nationally against “Pirates” is the 102-minute horror film “Bug”).

Further, Mr. Hartigan said the tendency of studios to rapidly green-light sequels for successful films (no fewer than 13 sequels are scheduled to hit screens this summer, and Paramount has already okayed a sequel for “Nancy Drew,” which doesn’t open until June 15) may inadvertently lead to longer sequels of lower quality. “Increasingly, if something’s successful, sequels are being green-lit and rushed into production as quickly as possible,” he said. “If the opening weekend numbers are huge, they want to rush the sequel, and that leaves almost no time for editing oneself or for filtering through everyone’s ideas. In the end, it means everything is getting put out there. What they’re not asking though is: ‘Okay, it’s longer, but is it better?'”