I, too, tend to ignore "sell by" dates. But I wonder if anyone else has had this experience -- Diet Coke seems to have a limited life span. I once found some in the back of the pantry that had to have been there for six months or a year. I assumed it was OK to drink. It was still carbonated, but it tasted terrible! I have experienced this another time, too. Anyone discovered the same thing? Wonder what makes it go bad.