I think instead of a "born on" or expiration date, they'd probably be better with a "best if consumed by" this way it's your judgement as to whether you want to risk the lack of carbonation or whatever.

Expiration dates mean nothing as the product can still be good. Case in point, Jones soda uses their dating system which means nothing to the average person, but they say their product is good for 2 years in a glass bottle. Where other vendors put 6 months out as being expired.

I think it more depends on the packaging. In a can, soda will eventually start to get the metal taste. In plastic, the carbonation eventually permeates through the bottle, thus why most bottles are eccessively carbonated ands till go flat in about 3 months. Glass however seems to keep it's flavor and carbonation for a very long time.

I'm currently drinking some Crush tropical punch that says it expired in December 2007, but tastes just as good as the first bottle I opened when I purchased them last summer.