This is helpful when it comes to knowing your dogs requirements with age.
Article by dr. K. Becker.
All of us who love dogs are acutely aware that the lifespans of our canine companions are short – much too short. And while the years we spend with a beloved pet seem to fly by, dogs don’t just suddenly die when they reach a certain age. They grow older in stages just as we do, but at a tremendously accelerated rate compared to humans. Your four-legged friend may still look and act like a puppy much of the time, but there are age related changes taking place inside him despite his youthful good looks and high energy level.
The lifespan of a dog depends primarily on his size, breed (or breed mix), and health status. As a general rule, giant breed dogs are considered senior citizens at 5 years of age, and dogs under 20 pounds move into the range at about 7.
Of course, every dog is a little different, but this is a good general guideline to determine your dog’s age in human years, as well as when he’s considered a senior, and the age at which he enters the geriatric stage of life