best light cycles for different stages?

[Dutch Pimp]

I want to know what the optimum light cycles are for the different stages of life in a plant's life.

I know 12/12 for when you want it to flower, but what about seedlings, small plant, almost full size etc.?

18/6, 20/4 & 24/0 vegging times work well. Your choice...whatever suits your personal schedule....