
Despite what all the books/Welfare organisations say about pups best being in new homes by a certain age I have always found the pups who stayed longer with their canine family have been the easiest in their new homes.
I think the books, Welfare organisations assume a bad breeder who doesn't socialise/train appropriately and experienced knowledgeable owners when they say a pup is best with it's new owners by 7 weeks.
Certainly in our breed in the USA most breeders want to keep the pups until 12 - 14 weeks to have longer to evaluate them, and it's tough if the owners want them sooner, though of course many will have to travel inter state.