I confess! I too believed the myth. For the record, I feed Kent (which i feel is a quality mineral)as well and have noticed the same thing. Sometimes they will flat nail it, then they just kinda shut off it for awhile. Pops cattle do the same thing. We keep it fairly close to the water source so it's always there for them. I understand what Anazazi is saying about the cows maybe being short and trying to increase their stores, most mineral producers actually acknowledge this. At the same time, you can't just assume the cows don't need mineral because they aren't eating it anymore. If you can keep them consistently eating the appropriate amount, you will avoid the feast and famine cycle. I clearly haven't perfected it yet myself. It's all a work in progress. Also, note that mineral needs change with many variables such as forages, what life cycle cow is in, etc etc..