Will Juvederm prevent lip wrinkles if I start getting it at age 19? Will my face be dependent on it?

Thank you for your question. Juvederm in the lips typically lasts anywhere from 6 to 9 months based on the average person. I would advise you to consult with an expert injector to discuss your expectations.

Juvederm can be applied to help enhance the volume of the lips, it's not a permanent filler and can last anywhere from 6-8 months. Seek a reputable injector who can provide the result you wish to achieve 

Juvederm or hyaluronic acid fillers can be placed in the lips at 19 years of age.  Restylane as well is a nice filler for lip augmentation.  Fillers such as Juvederm and Restylane have a temporary result, lasting for at least 6 months.  Hyaluronic acid fillers such as Juverderm and Restylane are made from a naturally-occuring sugar found in the body and provide a very soft, natural augmentation to the lips.  They, however, do not prevent wrinkles.

An injectable filler does not prevent future wrinkles from forming. It will just work to fill in the wrinkles that are present. Botox, however, can be preventative. For example, if an individual frequently frowns, the Botox can decrease the frowning, thus decreasing the lines that will appear in the future.
Juvederm is a great filler for lip augmentation. When the injections are performed properly, it yields a great looking and natural result. The Juvederm will not leave you dependent. I hope this helps, and I wish you the best of luck.

Juvederm won't "prevent" wrinkles per say, but can enhance volume if one has volume loss in a given area.  Juvederm in the lips will provide a more fuller lip, and I would recommend treatment with a board-certified dermatologist or plastic surgeon for treatment.