That's just all dogs and it's up there in the list of the saddest part of life. It's always living with the fact that yesterday he was a puppy and tomorrow you'll have to say goodbye, but today, today is the best day of all.
It's extra sad for large breed dogs, who live much shorter lives
True. Most "normal" dogs usually live 10-15 years healthy depending on the breed. I don't think I ever saw one of my parents' wolfhounds make it to 9yo, and that was with plenty of care and a healthy life. Being that big just pushes the limits of what their body can do.