There have only been two times in my life where I only had one dog and I always thought there should be two...it just seemed like something was missing. When I was a kid, we started out with one, but she had pups and we kept one so there was a two dog household from when I was very young.
I've had various numbers of dogs at different times in my life. A few years back I had 4 at a time. It was a tad on the hectic side, but really quite workable. It was mainly difficult to travel with all 4. Otherwise, we took off leash hikes mainly, and that made it easier than walking them on leashes individually or all together.
Now I'm down to the two Chihuahuas. They're really no harder than having one dog. They're so easy. I like that they have each other for buddies too, besides me. I enjoy seeing them play and snuggle...they get along so well. I have a feeling that if I were down to one, I'd be sorely tempted to get another. Two seems to be a good number for me. Although, maybe it would be wiser to just have one at some point because I'm getting older and lazier. One would be easier I guess, but I just don't like the dog to be solely dependent on me for companionship. I like being able to leave for a few hours and know that they have each other. I find these tiny dogs much easier than big dogs in most ways. It would be a different feeling to me to have just one....not sure if I'd like it...maybe.