Vicki,
There is not one answer that applies to this question. It depends on the jurisdiction, gaming laws / regulations and casino policies. Many are still good and redeemable for face value for as long as the casino exists. Others will not be if a casino has announced a redemption period which has expired. Keep in mind that the chip may have collector value in excess of face value before you think of taking it to the cage. You may get more in cash or trade than face value. The various chip catalogs can give you an idea of collector value. Post a message here if the catologs do not give you enough info or if you want help / opinions from other knowledgable collectors on a particular chip. Scans of the chip are helpful.
Paul