How long does tahini paste last if was never opened? There's no date anywhere that I can find.

I always put mine the 'fridge after opening.
When purchased it's very stable waiting in the jar,until you open it and expose it to air. Although you'll need to take a knife or fork and incorporate the oil on top like you would for natural peanut butter. Basically treat it like peanut butter. Shelf for short term storage after opening--'fridge for longer use.

Whoops, forgot to add the link http://www.bestfoodfacts.org/blog/post/tahini

Some manufacturers say not to refrigerate it, though I do. The only down side is that it hardens and it's tougher to stir. And here's someone who suggests two years as a shelf life. I've certainly kept it a year or so without it going rancid.

My advice would be to toss it out three months after opening, and yes it does need to be refrigerated. Meanwhile you can make a lot of hummus

I think it would last a year or so. But just give it a sniff test--you will know if it smells rancid. Otherwise it should be fine.