The coupon on the back cover of your direct-mail flyer is good for the whole sale promotional period... Then if they are having a special sale (like a Moonlight Madness / Firefly Frenzy / Daffodil Dash) ~ those coupons will have the sale dates printed on the coupon (valid Jan 23-29, 2011) etc.
The one sale name that will let you use lots of coupons is "Coupon Commotion Week" ~ but they are labelled "one regular item" or "one notions item" or "one craft item".
Have you also heard of "if they are from different sources"? Haa haa, you CAN use a 40% from the NPI (newspaper insert) and a 40% from your DM (direct mailer) and a 40% from your email signup all on one transaction.
Now to dispell some of the confusion:
If you use your 40% coupon on an item, and there is a special "10% off entire purchase" coupon, that 10% will not come off the item that used the 40% coupon (that's a double coupon). The 40% are limited and not good on certain items, like Cricut machines, sewing machines, Rowenta irons, patterns, etc. Those items are price controlled by the vendors.
If an item is on sale, it won't let you use a coupon. Yes, we used to be able to override it (if on sale for 30%, but you had a 50% coupon, we could override) ~ but they took that capability away about 4 years ago.
I was a merchandising mgr ~ I got good at explaining it to lots of patrons. If they were still upset, I could do a managers over-ride and allow an additional non-sale item "managers coupon"... just not on certain items (like Cricut)