So long as it doesn't smell rancid and has no obvious "bits" floating around in it then you should be okay.

Like all things organic, castor can be invaded by micro-organisms that cause it to be broken down.

Even Jet fuel goes off -- in fact jet fuel contamination is a *big* problem in some parts of the world and significant amounts of biocide are used to prevent the growth of bacteria that are happy to grow in what we might think is a very hostile medium.

If your castor has been stored in a cool dark place then chances are that it's okay but your nose and eyes should be able to confirm this.