I was thinking of phrases that are overused by the author. In this case, they said multiple times that characters 'screamed with laughter'. On about the 5th tim

I was thinking of phrases that are overused by the author. In this case, they said multiple times that characters 'screamed with laughter'. On about the 5th time this became somewhat jarring. You are right that in reported speech a specific character might repeat the same thing over and over. And that in stylised writing there may be stock phrases that are always used without problem. A good example here is the The Iliad by Homer, which uses multiple stock phrases to support oral presentation by a story-teller to an audience. Children's literature may use similar conventions (e.g. "Once upon a time...", "And they all lived Happily ever-after")