I have some hazelnuts that I toasted and then vacuum sealed a year and a half ago. I keep them in my dark cool pantry and the seal is still tight. I’d love to be able to use these instead having to run out to the natural foods store to buy more.
Is this a bad idea? I looked around online and didn’t find a definitive answer on toasted nuts.
Eat them unless they taste bad.
I tasted one and they taste fine. I’ve never eaten a rancid nut so I wasn’t sure if it was something I wouldn’t taste but would make me sick or something.
Case closed. 
Wasn’t the point of vacuum sealing and storing them so you could use them 1.5+ years later?
Rancid oil is something you can definitely taste. It’s a strong bitter taste where none should be. Also, eating rancid fats isn’t the greatest, but it won’t poison you a la botulism. If your hazelnuts taste fine, knock yourself out.