Why don’t you think your dog would be happy by itself? You’re placing a human emotion on a dog, you see wagging tails, lots of play, and so you think they’re happy. But what is happiness to a dog? My dog is never happier than when we’re at training and he gets to work. He’s also very happy when we’re on a hike, or playing tug. He’s also very happy to play with my other dog.
The problem is also that you’ve still got two puppies. One is an adolescent and the other one is really young. They’ve been together now for just a few weeks, and there haven’t been any issues. What happens when they start to mature? Develop different ideas of what’s alright and what isn’t? My boy was 3.5 when my other dog entered the picture, and she’s a rescue that was about 2.5 years old. They were definitely set in their ways, and it was actually wonderful because they are completely different dogs so they fit into our family really well without any fighting or battling for ranks. It also helps when the owners “know” what they’re doing.
Your definition of “obedient” might be completely different than what mine is or what other people’s is. Many people, even those with goals of trialing for titles will tell you their dogs aren’t at a level of obedience they’re happy with at a year old. So, saying a dog is done at a year old and now I can bring in a new one is quite the statement.
It sounds like the puppy has really attached to your older one. This will make obedience training a little more difficult as the relationship you’d probably prefer your dog to have with you, has actually formed with your other dog. This is another thing that people always warn about…but again, it’s based off of what most people on this forum expect from their dogs, some people could care less that the relationship is made with their other dog. From what I’ve seen with my dog is that at around 3 years old, playing with other dogs became not as important as it once was. So he isn’t as willing to initiate such a close relationship with another dog, therefore the second dog reads that and is more likely to try and form that relationship with me rather than the dog.
The reason 3 years is told to “novice” owners is that it’s hard to believe their first dog is that great in the first place. Then they want to get a second one, who will also probably just get a nice 8 week course in obedience and be “done.” Then 2 years later when both dogs are maturing, fighting for positioning starts because neither dog was ever properly trained. It’s these types of things that people give advice to prevent…not saying it’s not possible to have two young dogs, it’s just rare that it works out “successfully.”