Generally, you don't know unless you ask at the casino. Some promo chips have printed expiration dates but they aren't always refused after that date. Caesars Palace honors every chip made for play, even promo chips with exp date past. Others do adhere to the expiration printed. If the Casino closes or is sold, the NCV's are generally not honored by the new management, but they can be.

Remember, there are different categories of NCV's. Tournament chips are usually replaced every few years. You can't cash tournament chips anyway.

Free play chips are usually good as long as the issuing casino is around under the same ownership. Again, you have to ask, or just try to play them to find out.