Vitamin E DOES expire.
All vitamin supplements will begin to lose their potency after a period of time including vitamin E.
What Does the Expiration Date Mean?
Since 1979, manufacturers are required to stamp expiration dates on medicines and vitamins that will guarantee full potency, as well as the safety, of the product.
Does That Mean You Should Always Discard Expired Vitamins?
Interestingly, according to The Harvard Medical School Family Health Guide, this does not always mean that the drug or supplement should be discarded. The guide cites a study conducted by the military that found that many drugs were still useful years past the expiration date, but cautions that if you are interested in being guaranteed 100% potency, you may want to buy a new bottle. You can read the full report here to form your own judgment:
Why Take the Chance That It May Not Be as Effective?
The other side of the debate is that the point of taking your vitamins is to gain 100% of its value, which may or may not hold past its expiration date, which largely depends on how the product was stored. Since there really is no way of telling how much of the original potency a vitamin still has, it makes sense to use the expiration date as a guideline.