Mocha is a little younger than Sophie was when Bruce arrived. The one big mistake I feel I made was to let them have as much unrestricted play time as they wanted. This allowed Bruce to develop a strong bond with Sophie, and there were times he would look at her to see what she was doing when I told him to do something, and he would cue off of her. They would be playing bitey face and wrestling with each other, and wouldn't stop when I told them to. I had a heck of a time with that.
Sophie will be 4 1/2 when the new pups gets here, and she is now what I consider a mature adult. I plan on restricting and controlling the play time right from the start. Although I do think it will be a much different dynamic between Sophie and this puppy.