We had three dogs in my last house, one per person in a roommate situation. Mine, Anna, was a lab/chow mix I rescued from neglect as a senior (thinking she was 11 at the time). My roommate Rick had a young Beagle. They got along great, would even play and wrestle as best she could with arthritis.
Then I met my boyfriend, and he moved in with his huge Bassett Hound (Schroder) who is also a senior and had been an only dog all his life until then. Schroder loved it, he played and slimmed back down to a healthy weight, we all took care of eachothers dogs for feeding and bringing them in at night.
When we bought our house this year, Rick decided not to move with us, so it was just Anna and Schroder, two old farts milling around the yard and laying in the sun all day: however, they were both happy dogs.
When Anna died, I wasn't planning to get another dog for a long time. Heck, it's been months and I still get choked up like right now. But Schroder was a mess...I would leave for school and come home to him howling after ever class. I don't know what Mike did while raising him, but he had some separation anxiety as a pup too. I wanted to try being a one dog family, but once we went to the shelter just to "look" (my fiance is a crafty man!), I knew I couldn't leave without saving a puppy.
I was blessed with our GSD mix, Bentley, and it's been wonderful. But I also have a lot of time for them both as I only have classes for three hours a day, and Mike gets home while I'm in classes.
Also, in the long run, I know Schroder is getting older...a few more years...and I can't imagine our house without a dog, how empty it would feel.