does the value of a working dog increase over time?

Question

Is the value of a trained adult working (Livestock Guardian) dog greater than the value of that dog as a young puppy?

Answer 1

Of course it is, if properly trained. But it isn't age alone.

Just think of the amount of training that got invested and also other costs (food, medical care, etc.). A puppy is no real "working dog" after all.

The magic word here is "properly trained". A well fed guard dog that will just bark all day long or bite any stranger without provocation won't be considered as well trained/valuable as one that actually follows orders, is silent unless provoked etc.