Hey Cybertraffic,
I use PPS since the start , as for the retention I have never tried that option with SD but what I can tell you, is that I have been inside the members area and can tell you that there is LOTS of content that i spent hours on and don't forget once you get a password to the member's area you get access to all the other 60 sites for extra bonus !!
Also we do frequent updates on our sites, therefore you might wanna try the Recurring
