loftar wrote:It matters in that objects with different materials can't be instance-drawn together.
That being said, though, I guess I should add that I think performance should be a very small problem in the case of cupboards, since they are virtually always indoors and therefore 1) not in that large numbers, and 2) not competing with a lot of other stuff for render time. So out of all the containers, cupboards may actually be a fairly good candidate for variable materials.