Is every piece of trash they produce indistinguishable from the material of their buildings? Do they have invisible servants that do the laundry and empty the chamberpots, or are they perhaps too constipated to need chamberpots? (This last seems to be a common problem of fantasy elves).
And I might as well link this one while I'm at it.
No royal heirs raised as peasants. This is the plotline I hate most in all the world. It should be tied out in the desert, covered with honey, and left for ants to find.
"Waaah! I am adopted! Waaah! I am deprived of my heritage! Waaah! How evil the usurper is..."
And then Limyaael smothers the whiny royal heir with a blanket.