The manufacturer of Juvederm (Allergan) and other fillers do not recommend saving syringes. It is sometimes tempting to want to save a syringe to see what the outcome looks like after the swelling goes down (about 1-2 weeks); however, the risk of infection is present. We do not save syringes as a policy to reduce the risk of infection or contamination.
We have had some left over Juvederm from some of our injections and have seen that the residual Juvederm dries up pretty quickly. I am not sure that it would last the 6 months that you asked about in your question.
Hope this answer helps.

