the benzoin siam i have goes on strong forever, without losing it's shape. and obviously, musks. labdanum, patchouli, castoreum, civet. ambergris has a reputation of being very persistent, but i have never smelled the raw material. i suspect amber resin will last forever too, but i have only smelled it straight from the tree. i am planning to collect some and make a tincture, it smells great.
i suppose if the material is really thick or even solid, it will be usable as a fixative. am i right?