Marvel’s The Avengers will try to raise its gross tally by expanding to about 1,700 theaters on Labor Day weekend, its 18th week of domestic release. The worldwide gross is nearly $1.5 billion, already making it the third biggest grossing film ever. They’ll have to stay at that many screens for the rest of the year if Marvel hope to crack James Cameron territory: both Titanic and all-time box office champ Avatar did upwards of $2 billion. The film will continue to rake it in when the DVD is released. This franchise alone (a sequel is in the works) makes that $4 billion Disney purchase of Marvel look pretty smart.