Regarding expirations dates on supplements. This can be a tricky issue and one that isn't an "across the board" answer. Firstly, on the manufacturing end there are what is called overages. What this means is if there is an expiration date on the bottle and if the company is semi-reputable, the amount on the label has to be available at the time of expiration. All bets are off after that date. As long as the 400IU of E on the label is still there at the given expiration date they're good to go. In order to accomplish this end companies are allowed to do overages. Meaning, although the label says 400IU's it can actually have more in it at the time of production to allow for breakdown so that it meets the expiration date. Now some may think this is a good idea. I would argue that point as overages can vary widely. Some excellent manufacturers will have very short shelf dates on them because they DO NOT do overages. IMO this is a good practice. Longer shelf dates would most likely indicate they are doing very high overages. Not good.

The other issue with regared to expiration dates is that the expiration date really isn't relative to the expiration date of the raw source materials used to make the product. For instance, you can techincally manufacture a formulated product with a number of nutrients, all of which will have different exiration dates on the raw source materials used to make the formula. So in essence you could have a product that has an expiration date of say 05/05 when it may have been made with raw materials with expiration dates of 12/04.

Understanding the mechanics of supplements manufacturing is quite involved. Not only are the raw materials quality and testing an issues, but the manufacturing procedures are as well, as in standard operation procedures. All can affect the quality of a supplement.