I have a coupon programmed as an educational discount.
The coupon is not limited to one time use and is set to expire in 2015 though
I've tried other dates as well.
After about a month or so the coupon suddenly becomes invalid. The customer
receives and "Invalid Coupon" message at the top of the shopping cart when they
try to add it to the cart.
I'm sorry that there's not much info to go on but everything looks normal on
the coupon page.
I should have saved the state when it was invalid and I will if a check of the
source code doesn't show any problem.