That damned “Avengers: Infinity War” swallowed the last vestige of box office innocence with its record-breaking $258 million opening last weekend.

It’s earned $340-350 million in the U.S. alone. In a week!

Surely this cannot continue. Unsustainable. All that. I mean, “Black Panther” was a phenomenon, hanging onto audience for months as it marches toward $700 million, domestic.

So expect “Infinity War” to have a fall-off closer to the latest “Star Wars” movies, whose records it vanquished. A 50% drop is guaranteed, 60% more reasonable and if it’s not getting repeat business, expect even more of a plunge.

Box Office Mojo is figuring a 44% fall-off is a safe bet — $116 million or so. Use that as your benchmark. If it earns less than that, it’s starting to wane as Marvel fans brace for “Deadpool 2.”

Box Office Guru figures a slightly steeper drop, down to “only” $108 million.  I’m guessing that’s closer to the mark, low $100s.

Curious to see how Eugenio Derbez’s remake of “Overboard” makes out with his Latino audience here in the U.S. The movie’s dull, he has zero chemistry with Anna Faris and yet he’s popular enough to promise a $15 million or so opening weekend, prognosticators tell us.

“Tully” has another wave of enthusiastic Jason Reitman/Diablo Cody/Charlize Theron reviews, and should stick around for a few weeks. Not from me, but SOME folks are crazy for it. It won’t open big — $5 million would prompt champagne cork-popping at Focus Features. Theron isn’t big box office, and she’s not at home in comedy. I’m guessing $4, tops.

The badly-acted serial killer thriller “Bad Samaritan” is opening on more screens, and David Tennant has his fans. If everybody’s seen “Quiet Place” and “Truth or Dare” it could manage $5.