Why Don't Dermal Fillers Last Long?

The higher the concentration of Hyaluronic acid and the more cross linking causes the filler to last longer. Juvederm has the highest concentration of HA  at 24 mg/ml.  Belotero has 22mg /ml  and Restylane has 20mg/ml.  For most people Juvederm lasts several months up to one year. It may be that you have been undertreated.                                                                      The nasal labial folds typically take 1 syringe per side in some cases they need more. It sounds like you may have swelling that makes it look better initially but when the swelling goes down you lose some of the correction.  You undoubtedly still have filler present but it softens and may be difficult to feel. Try having more or switch to a different filler. 

Without knowing the details of your Juvederm and Boletero treatments, it's difficult to give you an answer as to why you felt your results only lasted a few days.  Most likely it's due to not using enough of the filler to give you a longer lasting result.  Both Juvederm and Boletero last a few months before dissolving.  There are other fillers that last longer, including Radiesse and Sculptra, so these would be other options for you as well.  

In general, most hyaluronic fillers should last 4-12 months depending on what concentration is used, how much is used, where it is placed, and how each individual patient degrades it. often times patients will say a product did not aceive the desired result, but it could be that not enough was used. In trying to contain costrs, the patient or the physician may be using less than what is actually indicated.