Drip-Content Module / Scheduled Delivery of Content for Member Retention

I don't even know if this exists - but I am looking for a way to drip content (in the form of both written content like articles and PDF files) into Dolphin using sequential scheduling.  I was hoping for a module that someone could install but maybe there is a way to tweak Dolphin to schedule/rotate content.

The problem I am having is that members sign up, get what they want, then leave the site.  Even if I uploaded and downloaded content manually, the sequences would be off because some members have been around longer than others.  I either need to be able to drip content to them on a weekly basis or just force them to buy everything a la carte so I don't lose money.  I would prefer to drip the content to keep them around and coming back for more.

WordPress sites use something called WP Drip (see http://www.wpdrip.com/) to accomplish this.

I have put a lot into my Dolphin site and do not want to start over with a WordPress site for this one reason alone.

Ideally, members would get a new article/PDF file every week.  New members would start with "Article #1" and go from there.  Older members might be on "Article #24" because they have been around longer.  I do not want both old and new members getting the same article each week.  I hope that makes sense.