I get the emotional attachment side but I just don't see the logic in it unless you've lost almost everything from that family of dogs and they were the best that you've ever touched. I've always felt that if a dog didn't produce something worthy of breeding to and moving forward with, it wasn't worth the effort to begin with and deserves to fade away. The torch should be passed on to the future not the past, or in this case, the ever present now(stagnation).