My male yorkie is 8 months old, too, and we are getting him a female friend that we are picking up tomorrow!!! We are very excited, although I did have the same apprehensions as you described. Although I am still a little apprehensive about the whole situation, I just know that I am going to love the second one as much as I love Hobbs. Everyone says that once you do make the decision and get a 2nd yorkie, then you will wonder why you didn't do it sooner!
Overall, I think the younger your first yorkie is, the better he/she will adjust to the 2nd yorkie. Hobbs is still in his puppy stage and just LOVES playing with other dogs his size. So I hope he is excited about getting a live-in playmate.
I'll let you know how he reacts in a few days!
