A good temporary exhibition can do more than stand on its own. Sometimes it changes the way you look at the rest of the museum.
It might introduce a theme, artist, period, object type, or historical question that suddenly makes the permanent galleries feel different afterwards. You leave the exhibition and begin noticing connections you would probably have missed before.
I think this is one of the strongest things a museum can do: use a temporary show to open a new door into the collection it already has.
Have you seen a temporary exhibition that made the permanent collection more interesting?
Did it help you understand familiar objects in a new way?