By her own admission, Anne McCaffrey had found Dragonquest (1971) very difficult to write, to the point where she more or less burned down the first draft and started again. Which understandably did not make her overly inclined to start writing its sequel—especially since she had other non-dragon books to write. But five years later she published a companion novel aimed at younger readers, Dragonsong (1976), swiftly followed by a sequel, Dragonsinger (1977), both set during the time of Dragonquest.
She clearly still had more to say about dragons.
This eventually led to a short story, “A Time When,” published by the New England Science Fiction Association in 1975, which McCaffrey expanded into a novel, The White Dragon (1978), one of the first science fiction books to land on The New York Times Best Seller list.