
So many factors to consider.
If the pups are not getting satisfactory socialisation (perhaps your breeders lifestyle and yours differ vastly, say you live on a boat etc
) .
If the mother is sick of the pups and they spend more time with one another playing the fool and getting no education from adult dogs.
If they are a large robust breed.
(and many other reasons),
Then no, 6 weeks is not too early, its probably teh best age.
If the pups come from a small litter, a physically small breed, fantastically socialised, their education with older dogs and younger dogs and a vast range of people, then staying until a few weeks older can be better.
That said, around 8 weeks old pups suddenly discover 'fear' and taking home a pup who has just learned to be frightend of stuff is not the best way of doing things!
Em