I have kept puppies with their mother up beyond 2 years. If the bitch is a good dam, it doesn't hurt the puppies at all to be with her.
A pup when it goes to its new home gets a boost of confidence, kind of like being thrown into the deep end, sink or swim buddy. (Yeah, that's probably a terrible way to learn to swim), but those that do learn to swim, get a huge burst of confidence. As it is with puppies at 8 or 10 weeks, they learn to switch their allegiance from their dam and litter to their new owners. It is the only thing they know. The person that brings the food and talks and plays with them, was talking to this person and seems to think they are ok, so, this person is the link to everything I know. And soon they are bonded.
And yes, it takes a little longer if the pup is in with the mom for 12 months. But for 12 weeks? No problem.
I personally think it is easier on the dam if she can wean them when she is ready, and then for the puppies to go 1-2 at a time. Having 5 8 week old puppies one day, and none the second day, is just hard on the bitch.
Heidi Ho, Odie
Joy-Joy, Bear Cub, Hepsi-Pepsi
Cujo2, Karma Chameleon
Ramona the Pest, Kojak -- who loves you baby?
Tiny Tinnie, Susie's Uzzi, Kaiah -- The Baby Monster.