Bones

Question
If you are in favour of giving a dog a large pre prepared bone from the pet shop, how long should you allow them to have it at a time?

My Dog is a Wiemaraner he is 7 months old

Answer
I don't know that limiting how long the dog has the bone is important other than taking it away if it gets gnawed down small enough to be swallowed or breaking and splintering.  

The dog guide school I raise puppies for forbids giving any dogs in their program any bones at all.  Their dogs do quite well without them.  Although the bones you asked about are less dangerous that many others, they do accelerate the wear on teeth.  Dogs don't need bones.