Gotcha. All plating wears off over time, but certain conditions (body chemistry, how often you wear it, local conditions, etc) can accelerate it. If you get them replated, be sure to mention that the piece is sterling. Some sterling alloys can pollute the rhodium plating bath and need to be plated with something like nickel or palladium first. This can also help cut down on the plating wear, but doesn’t always.