The results of fillers such as Juvederm Volbella/Vollure or restylane silk/defyne/refine can vary slightly from person to person, but the results generally last 6-9 months. Patients who exercise more or have fast metabolisms will have to do their fillers more often. Fat injections and lip implants can be used for those who do not get longevitiy with fillers. Alternatives to achieving a full lip are NOVA Threads, which can provide lift and some volume as well. I would suggest consulting with a facial sculpting expert to help you achieve your desired look.
The duration of lip fillers is quite variable. The product,Volbella, has a duration of up to a year however in clinical practice it is closer to 6 months. Fillers tend to resolve sooner around the mouth/lip areas since the area is very dynamic. Patients who workout often and have a high metabolism tend to retain filler for shorter durations. Volbella is a nice filler for lip lines and definition of the lip border however it is not my first choice for plumping/volumizing the lips. Perhaps you would get longer duration if you used a combination of fillers for lip enhancement. Please consult a board certified dermatologist or plastic surgeon experienced in fillers. Best wishes.