The main thing to remember is that when they scan your coupon, it keeps you "active" in their records. If you don't use the coupons for a certain length of time, they drop you.
My sister is with the American Red Cross and spends a lot of time overseas, usually for 4-6 months at a time. Her husband sends me her JoAnn flyers, and I use her coupons, so she won't get dropped from their system.