A As per the manufacturer guidelines, the reconsitution of neuromodulators is strict and should be followed by each trusted practitioner.
However if you are concerned about the longevity of the treatment, there are some new serums/creams you can purchase from a medspa/derm/plastic surgery clinic that offers these.
The serums/creams can be used alone or to work synergistically with the injections to provide longer, lasting results. Ask your practitioner next time if you can add one of these serums to your regimen to get longer, lasting results.