Ive just gone through my jars(of which there is a lot!) and 4 are past their sell by date. How long is the shelf life and will these definitely be unusble?
Herbs and spices are one of the only things where the shelf life is usually too long but best way is to open them and smell them if they are even slightly musty smelling then dump and replace. I only buy very small quantities as they lose their flavour so quickly
They wont be unusable, just less powerful than new. I just got back from Grenada, with fresh nutmegs, cinnamon sticks and cloves. This made me review my herbs/spice cupboard and last week I threw away 20 of what I had. Just smelling them you could tell they were no longer contributing much by using them.
When I cleared my stepmother's kitchen out after she died, I found nutmegs that were bought pre decimal. I haven't used them all yet, but they are still strong smelling, yummy.