Looking at my stats, 50%+ quit after the first month on most sites (with 50% being really good, seen sites with around 90% quitters, not counting trials).
I doubt that it's about content only, the problem is that many people will download as much as they can in a month and maybe come back half a year later to do the same again...not really a problem with super fast connections and download managers.
Those who stay longer are real fans, they stay regardless of the pure ammount of content, as long as there are regular updates...I advertise a site in a microniche that does 1 picture series and 1 single movie update every week, loads of members stay 6+ months. That's probably the reason why there are so many single girl sites popping up over the last two years, guys that fall in love with their virtual girlfriend are loyal customers.
So, content is king, but the formula "The more exclusive quality content, the better the rebills" is too simple.
