Have you ever had a craving for salty chips, gotten your fill and found the smell or taste of those same chips is suddenly off putting?
Another example is consuming human cell salts and that's the closest parallel I can find to explain how it is with animals. If your body needs a particular cell salt, it will taste sweet and desirable to you.
My naturopath instructs her patients to consume a cell salt until it no longer tastes sweet - that's your body telling you it has enough of that particular cell salt.
It works identically in livestock. When they are deficient in a certain mineral, that mineral will taste good to them. When they've had enough, it no longer tastes good.
This concept is sound with the Free Choice mineral system because there are no taste enhancers or additional ingredients they might want to consume purely for taste.
Again, looking at my own herd's consumption, you can clearly see that they will consume a particular mineral for a time, then stop for a period before often picking up that same one again in another month.
We're approaching two years on this system with consistent results. There is simply nothing "tasty" to drive over-consumption in this system, though I have heard reports of consumption concerns with other buffet style minerals.
My discussion here is based solely on my experience and research into the Free Choice system, which is unique among the buffets.
(As a fun aside, I am working on personal mineral deficiencies and the ones I know I'm deficient in are the minerals that smell appealing to me when I'm filling bags.)