Characters
Stop wearing out that mirror!
— Marion · The Adventures of Priscilla, Queen of the Desert

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The command imagines a mirror as something that can be exhausted by too much use. That exaggerated possibility makes repeated attention to it the subject of criticism. The line does not explain what the person is doing there, but insists that the use has gone on long enough.
Context reviewed