If I give you the precise duration overtone is expected to use on your hair before it fades or how often you have to wash it to fade, I will be getting your hopes high for nothing. This is because how fast they are expected to fade depends on factors like the porosity of the hair, starting shade, how often it is applied and the overtone product used. However, do not expect your overtime to be fade off at one wash as it can take several washes of at least 20 times, or weeks, or may never even come out completely unless you wash bleach. And that is why it is often difficult to establish a straightforward answer for questions like this.