I've always used expired BBB coupons with no problems. You can use either 3or 5 at a time(can't remember which) as long as you have that many items. I was also told by the Triangle Towne Store that if you make a purchase and don't have a coupon, but happen to get one in the mail later, take it in with your receipt and they will credit the 20% to you.
Yep... a woman in front of me in line at the BBB in Cary gave me one of her coupons when I didn't have one. It was expired and it worked!
