Once a customer spends $500 or $1000+ in a rolling year and has earned the Silver or Black tier status, there are spend minimums the following rolling year that are required to remain in this elevated tier. Each customer will need to spend $250 the following year to maintain Silver status and $500 the following year to maintain Black status.
If this does not happen, each customer will revert back to the appropriate tier status and will still be able to earn points.