
I think it depends on the pup. My 7 1/2 week old pups get theirs dry now, with just a splash of water to stop them scattering it everywhere (good game). I have had other pups where I have soaked it up to 12 weeks.
I gradually change from soaking a good while before feeding with quite hot boiled water, then I just put warm water on just before feeding, then use a little cold, and finally once opn their won fed it completely dry. I often put a bit of dry in a dish for pups to nibble at night when they are 5 weeks plus.