How long can baking cocoa last?

Normally high fat products go rancid because of oxidation, but chocolate contains flavonoids that hinder oxidation. According to ShelfLifeAdvice.com, unmelted chocolate can last anywhere from 18 months to 2 years, but I've found that the powdered form loses its taste before that time.

Taste some and see if the taste is still as expected and you should be able to make a decision on whether you want to use it.