I went to Linens & Things yesterday and had one of their (expired) coupons. So far the policy was that they accept their coupons even if they are expired (no matter how long ago) and they also accept Bed Bath & Beyond coupons as long as they are not expired.
As of last Saturday the policy is that they will accept their own coupons only up to 60 days past the expiration date. So if you've been hoarding those "20% off your entire purchase" from December, they are no good, and you might as well just throw away all the others that are over 60 days...
In any case, please check with your local LNT first and post your experience in this thread....
I went to the LNT on Empire Shopping Center in Burbank, CA.