How long does tahini last past expiration date?
For what it's worth, you can safely store opened sesame oil in a refrigerator for one year (stilltasty.com).

Peanut butter can be kept for 3 months in the cupboard, then another 3-4 months in the refrigerator.

To be safe, I'd say keep it refrigerated once it's been opened, and use it within 6 months. I've had some for about that long, and it's just fine still. 

Remember: bad odors indicate bad food.