I used to share a membership w/ my SIL, about 10 years ago. But, since she was primary, she was the only one who got the coupons. So, even though I asked to see the ones she didn't use, never got them. When she didn't pay her turn to renew, I just got my own.
With the amount of coupons I now get in the mail for products I already buy there, it ends up paying for the membership.