If you use d-limonene to dissolve support and you want to stretch your quantity a bit further, here's a trick you can use.

Take used limonene, pour it into a container (e.g. a mason jar), and stick it in the freezer overnight. Limonene will not freeze (its melting point is -74 C), but most of the dissolved polystyrene will precipitate out and form flakes. Take the container out, wait some more for flakes to condense at the bottom, then pour off the remaining clear liquid. If you have too much time and you repeat this process a few times, you can get all the polystyrene concentrated into sludge with consistency of sour cream.