Whether you're a responsible breeder facing the question of when to retire your dogs or you're looking for a puppy - age matters.
Generally speaking, toy breeds and other smaller dogs (Chihuahua, Yorkshire Terrier, Maltese) are considered to be senior if they're 10 to 12 years or older.
With large/giant breeds, the span of when your dog is considered "senior" is shortened to 5 to 6 years.
In theory, a healthy male can produce litters until old age. Most clubs recommend retiring a male after 10 to 12 years.
A healthy female can legally be bred until 8 years according to most breeding clubs. However, it's best to retire her after 5-6 years to avoid complications for both the mother and the pups.
Females