How long does tahini last past expiration date? I have a jar of organic tahini which expired one year ago.

It smells good and tastes ok. I don't know how it was stored, it was however always sealed (but already opened).

Is it safe to eat in large ammount ?
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.