I am in your shoes as far as introducing another dog to our home when I have done one at a time before. I did grow upIn a home with multiple dogs 1 1-2 years apart minimum seemed to be best. MY parents introduced a puppy to a four year old this year (both shelties). Twice they have had a collie with shelties. The sheltie being the older dog. Both great breeds. My pup is hitting 1 1/2 and i am thinking anyyime in the next 2 years to introduce another dog. I am thinking i want him a little further in obedience training as he is just ready for distraction work and getting maturity. I am hoping anywhere between xmas and next summer as ideal for me.