My Grandad, a farmer drilled me as a child for playing with the farm dogs and having a dog to 'just pet' was not considered. I think dogs are a good addition to all ages provided their purpose is clear, and their needs are planned and accounted for. To this day I still struggle to coochie coo non-working dogs and do not have them as pets. That is not to say I don't believe in their benefits with respect to human psychological health as well. Such an interesting topic.