This is an old post, but others may find it useful. Once a coupon expires (or not going to be used), you can send them to Coupons for Soldiers where soldiers can use them up to 6 months after their expiration date.
http://www.frugallivingnw.com/coupons-for-soldiers/It takes a little effort and a little stamp money, but it can be a big benefit for our soldiers and their families.