How long after expiration date can you use betty crocker cake mix and icing?

It's all chemicals anyways... I'm pretty sure that stuff would last for decades in a cupboard. It's really not good for you; not that homemade sweets really are either, but at least they don't have all the chemicals and additives. I look at it this way, if I can't pronounce it, I don't eat it (and there's a lot of stuff in those cake mixes I can't pronounce!)