well I dont think much bad can happen to mimosa powder, the max that will happen is oxidation of dmt to n-oxide, but if you extract with more polar solvents than naphtha, or do the zinc conversion, it shouldnt be a problem..
But anyways I think its much nicer to have some little glass vial with some nice fumarate ready to ingest or freebase (and it wont oxidize), than space-taking mimosa powder that whenever I want to use would still have to be worked on
