I haven't received any more than the usual one or two a week, but if I had to guess, I'd say that they're simply sending out multiple emails to anyone who has ever been on their mailing list, in hopes of increasing sales.
Someone correct me if I'm wrong, but doesn't it cost them just as much to send out (let's say) 100,000 emails as to send out 10,000? (I can't imagine the cost is much regardless of number, just whatever resources are used in maintaining the email list, the emails themselves cost nothing.)