Silver plated jewellery findings, such as pendant bails and chains, were developed to be a cheaper version of items that would otherwise be solid silver. Silver plating is commonly just a thin layer of silver applied over a base metal, such as copper or brass. This layer is usually quite thin and thus silver plated items will have a limited lifetime as silver objects. Eventually, the plating will wear away exposing the base metal underneath, though this can still be quite attractive.
Some like the soft coppery silver appearance of worn silver plate, and even the eventual full copper appearance when the plating is gone completely. If you are not a fan of this look, then you should not purchase silver plated jewellery or any other silver plated item.
If you take care of your silver plated item and never use any abrasive cleaning methods, you should get a reasonable life from the item, however be assured that the plating will eventually wear off. A search of the internet will provide a number of solutions to cleaning your silver plated items with care.