Check your render settings when saving. carrara will save a thumb at what settings you are using; see where it took an hour and a half to save a simple scene set for a hirez render with HDRI and SSS hair lol

Figured out my issue. Carrara does not drop the scene when you close the scene, open and close 3 or four scenes and carrara is cloging up your ram with every one of them.

Note to self: close carrara between scenes.