I know that my daughter's sheltie took a long time to get length to her coat. She turned 4 in August and finally has density and length. There is a Terv out there that seldom has a coat to speak of but is a multiple best in show and best in specialty show girl. Her undercoat thickened when she was spayed but she never got length. There could be underlying causes such as thyroid, food etc. but chances are she is genetically programmed for a coat that is much more old school that we see in the ring. You'll appreciate it if you ever do herding!
