Everywhere I have seen the G or G2 powder it is either already expired, or about to expire. Either this stuff has a very short shelf-life or it is not very popular.
I'm not sure why it would have a shorter self-life than the liquid. 
Interesting information:  I checked a box that I bought last year.  It shows the packaging date on the bottom, Feb 07 2011 @ 21:30 by XXX which makes sense since I bought it in March.  I looked for an expiry date but found none on the box or packets.  Perhaps you misinterpeted?  Another google search said that the powder has roughly a 2 year shelf life @ 70*F.
FWIW,I think expiration dates are really a marketing gimick for the most part so that storekeepers keep only the freshest product on the shelf.  "Best Before" would be a better interpetation.  Milk would be a definite exemption for me and I won't drink it after it's date unless I wanted to get sick.