Recommended number of lamps for toon shading?

Hi, I’ve been testing toon shaders in blender for a while now and always wondered how many lights or lamps I should use for toon shading. Normally,I just use one sun lamp for majority of my toon renders.

Usually one or two works well. Anymore than that and the toon shader tends to loose its’ dynamic effect and starts to become strange. Although there are exceptions to every rule depending on the style you are trying for.