I can only quote NV gaming regs.
In order for a casino to make a chip obsolete they must run a 120 day redemption notice in the newspapers.
Most casinos will run this notice when then change hands or just change racks.

Not all casinos will recall chips.
Example: Fiesta just changed hands but did not recall the old rack chips therefore they are still redeemable.

Example: Caesars has never recalled chips when they issue new racks. All chips issued since it opened are redeemable. BUT, many are worth far more to us than the redeemable price.

Example: The Horseshoe has never issued a recall but they will refuse to cash in old chips. They are technecly in violation of NV regs.

Like Phil said, there is not just one answer to your question. Best to come here and ask before you make a mistake. I suggest you buy The Chip Rack but still ask questions as a lot of things happen between yearly issues.