If we say that quality these days considers sharp, high resolutions images and same to the videos, its year 2006 - I presume that most of pay sites today (or at least bigger ones) has exactly that - rebills are yet poor.
I think that design/layout of site are not playing big roll once the surfer pay to enter. He won?t rebill to adore your design ? porn is the thing he is interested for, and sure, making him easy navigate site is a plus, but I think not the crucial thing. Even if navigation is complicated, he will once go thought it and finally learn how to use it, at least, he has 30 days to do this. Maybe one of the reasons could be lack of personality of a site? If you give him porn, a jerk off material, which is nothing else then blowjob-fucking-cuming (order can be different
in various scenes while hundreds of sites out there is offering the pretty much same thing (lets assume the same quality) ? why he would rebill at your site? Speaking about personality, aren?t solo girl sites trying to offer exactly that? It would be interested to know their rebills.
Another aspect could be developing of technologies and more percentage of surfers using fast connections today. With that type of connection, surfer could download hundreds of GBs to his hard drive during 30 days, basically rip all your site, and why the hell he would like to rebill? But, combining personality with constant updates on your site, I guess you could do something about it.