Thank you for a very good question. There is a ton of fillers on the market currently and the answer depends on the type of product that is used. The type of product used depends on severity of the smile lines, meaning how deep they are. For very mild smile lines, I often use Restylne Silk or Juvederm Volbella or Juvederm Ultra, which should last between 6-9 months. For Moderate lines, I use Juvederm Ultra Plus, Emervel/Restylane Refyne, which should last 12 months. For severe lines we have Emervel/Restylane Defyne, Restylane Lyft, which will last about 12-18 months. In April 2017, Juvederm Vollure will be available to smile lines and should last up to 18 months. This is a lot of information and every physician has their favorites to use and it honestly depends if you really need to have your lines treated versus treating what causes those lines to appear in the first place. You need to trust your face to an expert and you always want an unperson consultation. Hope this helps. Best, Dr.Avaliani