At 12 months, they are no longer eligible to show in the puppy class in a dog show, but Dobes (and other breeds of a similar size) aren't fully grown physically until around 18 to 24 months. Mental maturity, well..... that's another matter entirely. I'm still awaiting delivery of my 18 month old GSD's brain.

 

At our house, you are considered a puppy until we get another dog. Our current puppy is almost 2 years old now.

 

Both my dogs are "puppies". The youngest is a year and a half and the other is going on three.

Seriously, though. I'd say 2-3 years for full maturity in larger dogs. The cut off for "puppy", though, is a bit subjective. For me, any dog over a year old is no longer a puppy, but rather a young adult.