Directing a movie sounds tiring. Wrangling all the actors, managing the crew, resisting the craft services table – and making sure your vision comes to life without the help of the computer graphics that will be added in later. What sounds even tougher is doing all that with one of the biggest casts of huge stars and most complex and CG-intensive action sequences in any movie, well, ever.

And that’s where the Russo brothers, who directed both Captain America: The Winter Soldier and Captain America: Civil War, as well as the upcoming Avengers: Infinity War and untitled fourth Avengers movie, are at right now.

At least, that’s what it sounds like coming from Thanos himself, Josh Brolin.

“I think they’re in a position very openly and rawly where they’re like, ‘We would never do this again. This is a one-time deal. To put this many successful actors together is such a pain in the ass, but it’s been worth it. We’re doing two movies, one back to back, and this is it for us. Then we’ll go off in another direction. But this is a very, very, very ambitious project that I think is going to pay off in a big way.”

Does that mean the brothers, who have been Marvel’s most frequent collaborators to date, and arguably most successful, are done with the comic book company and movie studio after this? There’s no word on that – they could stick around to work on some smaller pictures. Maybe they have a character they’d love to see brought to life, and the success of Avengers: Infinity War could be the bargaining chip they need to make that happen.

But maybe they’re just tired of making movies on this big of a scale and want to make something smaller, and without a CGI budget that could feed a small country for a year.

But if there was ever a time to leave, this is it. Speaking to Variety, the Russo bothers have called the duology of movies “the final chapter of a book” written over a 10-year period, and that these movies are “a culmination and completion of one road.”

Neither Marvel nor the brothers are likely to confirm such a thing until after Avengers 4 comes out, and that’s just getting started in production. Avengers: Infinity War will release on April 25, 2018, with the sequel hitting a year later on May 3, 2019.