Marvel has built a vast media empire on the strength of such stars as Chris Evans, Robert Downey Jr., Scarlett Johansson, and Chris Hemsworth, but no actor would be content with playing and re-playing the same role forever.
But as Evans noted, they trot out a new James Bond every decade or so, so why not?
Downey is far closer to reaching that point where he may walk away. And I don’t know how you replace Downey as Tony Stark.
But a new quote from the actor suggests that he may not be the first big name to make a departure from the Marvel Cinematic Universe.