If you are working with your dog consistently and he is well socialized, there's no reason to think you can't be successful showing him at a relatively later age. Some people, myself included, feel that it's not always the best idea to start showing a puppy too young as most of the time, they are still immature and not ready to truly compete. Some people like to start entering them young for the practice but it can quickly become expensive practice with the amount that entry fees are now, although some clubs offer a discounted entry fee for puppies.

Jay