Wow, there are some really good posts here.
I have also considered a pal for Copper. Seriously like you. He loves other dogs...but there are other considerations, many which have been mentioned.
1. Expense is one...when all goes well, not so much but if a problem occurs...
2. Portable...I took Copper and his x-pen with me when I went to my daughter's house. She just had a baby and I needed to help with the other 2 children. Copper was easy. Just one little dog and the kids enjoyed him with supervision. Two would have been an adventure. I also took Copper to a friend's house yesterday (he was invited too!) and we watched a movie together. Copper kept an eye on her cat...funny...
3. Hubby is not really an animal person, but if I run out in the evening for something, Copper is always curled up in Charlie's lap while he watches TV when I get home. (I personally think they both enjoy that time.)
4. Copper is very attached to me which I needed and love. My brother comitted suicide last year, the day before my birthday. My family's world came to a stand still for a long time. I started reading Yorkie books because I couldn't concentrate on novels. They were a happy distraction and I started dreaming about owning a yorkie. Through a wonderful series of circumstances I ended up with a breeder and at 11 weeks old Copper came home with me on my birthday this year. 1 year after my brother's death. I have enjoyed nurturing and caring for this little dog. He has brought me so much joy after a year of grief. My brother was incredible at training dogs and won some awards for his field work with goldens...so I remember this often.
One dog...it works, why mess up a good thing?
I totally understand the desire for another...didn't someone say they are like potato chips, you can't have just one...
But...again, why mess up a good thing?