Generally, these purebred canines reach their full size at the age of twelve months. Some Airedales reach their adult weight even before then – at eight or nine months of age. However, you should take into consideration that these canines reach their mental maturity between 18 and 24 months of age. A two-year-old Airedale dog is considered to be fully grown. Still, there are several factors that impact the size of this large terrier. First, its dietary habits are of extreme importance. Dogs that are fed with poor-quality dog food or table scraps tend to be obese, which makes them prone to diabetes and heart failure. Consequently, overfed puppies are generally bigger than expected. On the other hand, dogs with certain health issues, such as thyroid disorder or cancer are most likely to be smaller than their healthy counterparts.