Yes, I noticed this kind of behaviour... I'd like to open an issue but I'd want to better verify this "leak".
To use a more lightweight approach, you could load it only on a single orbit:
var clouds = GlobalDirtEffect(\global_mi_clouds, [\cloudspitch, \cloudspos, \cloudssize, \cloudsdens, \cloudstex, \cloudswet, \cloudsgain, \cloudsspread, \cloudsrvb, \cloudsfb, \cloudsfreeze, \cloudsmode, \cloudslofi]);
var verb = GlobalDirtEffect(\global_mi_verb, [\verbwet, \verbtime, \verbdamp, \verbhp, \verbfreeze, \verbdiff, \verbgain]); \sawresonance, \sawpan]);
~dirt.orbits[0].globalEffects = ~dirt.orbits[0].globalEffects
.addFirst(clouds)
.addFirst(verb);
~dirt.orbits[0].initNodeTree;