we find that jwb on it's own isn't enough to firm up barkley's 'deposits' so we compromise by giving him half jwb and half nature diet (a wet food with ground bone and veg in it) for breakfast, and then all jwb (in a treat ball or scattered about) in the evening. that's been enough to firm everything up nicely.
if barkley was fussier though, this may have not worked as he clearly looooves the nature diet and could easily have gotten fussy and refused to eat the jwb on its own. however, he seems to munch it very happily and we find it easiest at the mo. i do plan to gradually vary his diet with more BARF though, and he gets extras like veg and cheddar cheese quite regularly.
can't remember when we switched him onto the junior variety but i think he was probably about 7 months old. it's nice coz the bits are chunkier and barkley certainly prefered it to the puppy variety. interestingly, though, it's only the lamb variety that seems to suit him.