Hello from Ottawa. Hopefully you are surviving the cold like I am (barely). This is a question cosmetic surgeons and facial plastic surgeons get asked relatively frequently. Often times there is a slight bit of confusion surrounding this as Botox is thought to behave this way. With Botox, it weakens muscles so over time, the muscles continue to get weaker and thus you need less medication to get the same effect. Think about it like lifting weights, if you stop using your muscles (ie stop lifting weights or get Botox) your muscles become less powerful and thus you don't have as much muscle to treat!This isn't true for fillers. Fillers simply take up space in your skin. However, people may get fillers and they notice it starting to go away 8-12 months later and come back in for some extra. Its not that you need less, its just that the old filler hasn't completely been dissolved yet. This can be a problem as now you set up a schedule where some filler is new, some is old and some is in between. This can cause some people to find the treatment is never perfect as the filler is always in a state of "Flux" shall we say. Everyone is different and some people like this. Feel free to come in and chat here in Ottawa if you ever have any questions,James P Bonaparte, MD, MSc, FRCSCOtolaryngology - Head and Neck SurgeryFacial Cosmetic and Reconstructive SurgeryOttawa, Ontario, Canada