It goes in cycles for me, but since I started stacking my smelter products and also not reserving any one smelter for any one type of ore, I really don't pay attention to which ore is "rare" at the moment. I used to reserve each smelter for one type of ore, but nowadays I mix them up a bit if I find I have a lot of one ore on hand but not much of another. Looks pretty all mixed up on the tables, and my machines never stop working anymore, plus now that I stack I always have bars on hand for making jewelry.
Which I never make anymore because I seldom receive truck orders for jewelry anymore. :(
