For about how long did the crowd in the Ephesus theater keep shouting praise to their goddess?

Answer: About two hours

When they realized Alexander was a Jew, they all shouted in unison for about two hours, "Great is Artemis of the Ephesians!" (KJV: Diana).

“But when they realized that he was a Jew, they all shouted in unison for about two hours: “Great is Artemis of the Ephesians!””— Acts 19:34 (BSB)