When I started my extreme amateur site I only had around 5,000 pics and 100 vids, plus heaps of bonus content. I did have trouble with the speed of my hosting, and maybe that had an impact but I did find that a large % of members cancelled almost straight after joining.
Now that the hosting has been fixed, and we have increased our exclusive pics and vids to over 15,000 (growing weekly) the members just don't seem to want to cancel, and if they do they come back after a month or so.
I am lucky that I can shoot all the content that I need myself, and if I did not have that luxury I would not be able to operate a paysite successfully. It would just be too hard to get hold of the content needed to keep the surfers happy...
Spooky