It usually takes a while. Tucker's tail really started blossoming at around 6 or 7 months old. Goldens don't achieve their full adult coats and feathering until they around 2 years old and some even take longer than that.
Bogey is going to be two and still has practically no tail. I trim it every 10-14 days to encourage growth and bathe him regularly, but some dogs just don't have big tails. You could ask your breeder, if you are in touch with them, about the dog's parents and when they got their tails.