Fanboys are plotting all-nighters for the debut weekend of “The Dark Knight Rises.” But even with around-the-clock playtimes, a record three-day domestic opening may be too high a ledge for Warner Bros.’ final Batman outing to reach.

Standing in its way is Disney-Marvel’s 3D behemoth “The Avengers,” which smashed Stateside opening records earlier this summer with $207 million.

Observers estimate that “Dark Knight Rises” will top out at around $175 million through Sunday, making it the second-highest domestic opening ever and the biggest 2D bow ahead of 2008’s “The Dark Knight” ($158 million). Warner’s “Harry Potter and the Deathly Hallows: Part 2” currently holds the No. 2-ranking domestic opening, at $169 million.

There’s still more than an outside chance that “TDKR” could surpass “Avengers,” given the voraciousness of its fanbase and more than $25 million in pre-sales. Batman so far is outpacing “Avengers” in advanced ticket sales, according to Fandango.

But consider three primary factors before placing any hefty bets in favor of “TDKR”:

Darker themes and more competition mean a more modest family turnout.

Christopher Nolan’s more realistic and violent — albeit relatively bloodless — take on the Batman story isn’t likely to draw the same kind of all-out family crowd that “The Avengers” attracted with its stylized action. “Dark Knight Rises” should lure plenty of parents with teenagers, however.

Parents also may wait for the fanboy frenzy to die down slightly before taking the tots, much like they did for “Avengers.”

As with the Disney’s blockbuster, “TDKR” has the weekend to itself among wide releases, though “Avengers” bowed with little in the market to tempt families. Batman will compete for that demo with three major studio toons, led by Fox’s “Ice Age: Continental Drift” in its second frame.

A lack of 3D means no premium upcharge.

“Avengers” grossed approximately $35 million of its $207 million opening from 3D surcharges, an average bump of $3.50 per ticket domestically. That means without stereoscopic dividends, “Avengers” would have earned around the same as most projections for “TDKR.”

The Batman finale boasts the widest domestic bow ever in Imax, at 332 sites. That said, “Avengers” also had support from the megascreen exhib (in 3D only), contributing 8% of the pic’s total Stateside opening.

“TDKR” in Imax is drawing considerable notice online, however. According to a Fandango poll, 62% of moviegoers who bought tickets for “TDKR” were excited by the nearly one hour of footage shot in Imax.

A longer runtime means fewer and/or super-early screenings.

In an attempt to manage the film’s almost three-hour runtime, exhibitors have added screenings starting as early as 3:30-4 a.m. on Friday. Some theaters will play the film continuously throughout the weekend.

While early-morning screenings should satisfy the franchise’s most avid fans, it’s possible that borderline enthusiasts will wait until next weekend if the more convenient showtimes sell out. A Stateside location spread of 4,404 will be able to accommodate most filmgoers, however.

“The Avengers” debuted at 4,349 Stateside engagements, but that pic also was shorter by 21 minutes.

The longer runtime for “TDKR” should have little to no effect on the pic’s playability. Consider “Titanic,” which at 194 minutes became the No. 1 grossing film domestically, to be surpassed by “Avengers” and “Avatar,” at 162 minutes. Early reviews for “TDKR” have been mostly positive; fanboy chatter will drive repeat business globally.

Warners launched “TDKR” day-and-date in 17 overseas markets, totaling approximately 6,765 screens. Australia and Asian markets including South Korea and Taiwan launched the pic Thursday, followed by Friday bows in major markets including Spain and the U.K.

“The Dark Knight,” meanwhile, earned $41.5 million during its debut weekend overseas, from 21 markets (excluding the U.K.) and 4,600 screens.

Stateside specialty auds looking for an alternative to Batman may turn to Magnolia’s docu “The Queen of Versailles,” which launches today at three locations in New York and L.A. Lauren Greenfield won the docu director prize at Sundance for the riches-to-rags story of a wealthy Florida family trying to build the largest house in America.