Aging in pets is a gradual process. Giant breeds tend to age early, for their life expectancy is generally less than 10 years. Large and medium-sized breeds have a life expectancy of 11-14 years, and small breeds can live 15 years or more. A strong, healthy dog will probably age later than a dog that is stressed by disease or environment early in his life. Dogs that are spayed or neutered before six months of age ordinarily live longer than dogs that are kept intact.
You can know that your dog is aging when:
He shows a general decrease in activity level
A tendency to sleep longer and more soundly
Waning of enthusiasm for long walks and games of catch
Loss of interest in the goings on in the house.
Extreme temperature effect him & he gets stiff legged at times.
He/she suffers hearing loss or partial loss of sight
Wounds heal more slowly
Skin loses pliability and the capacity of the oil-producing sebaceous glands diminishes.
The immune system is less able to fight off attacks of bacteria & viruses.