Interesting that they had expiration dates and didn't observe them; more interesting that they are now trying to ease their customers into using the coupons in short order with these new multiple expiration dates.
Reformed (and retired) marketer here.
The program must be working well for Bed, Bath and Beyond.
The coupon gets another buyer (me) in the store. Once there, I will:
1) Buy at least the one item at a 20% discount
2) Likely buy more than one item on my since I am already there (Oh yeah, I need a new colander or AA batteries)
3) See many more items I might want since they have a racetrack layout that forces me through the entire store
4) Remember them when I need something else home-related
Ultimately, I give them a profitable blended margin across multiple visits.
The expiration date(s) gives me a sense of urgency. The practice of accepting expired coupons lets me feel like I'm 'beating' the system.
It is a relatively cheap customer acquisition tool, especially in an economy where people are looking for a bargain.
In any case, I am certain BBBY has a system/team that monitors the program, analyzes the traffic generated, tracks coupon usage (bar codes) and shows it is profitable for the company.... Otherwise they wouldn't do it.