How often do aircraft get an external clean?

[AerocatS2A]

Originally Posted by the_flying_cop

We used to wash our fixed wing and helicopter ourselves (by hand) every Sunday. In fact, when the fixed wing was new (2002) and during the Commonwealth Games, we washed her twice a week.

You know you've "made it" in aviation when you don't have to wash the aeroplane anymore. There is a no man's land though where you realise that no one is washing the aeroplanes.