The problem with subscription sites like that is that paying for a month's subscription gives you access to the entire backlog of the work that a person has been doing for years. There's only so much that an OF model is gonna be able to do in terms of posing before they've done all the angles that someone would want to see. Why pay for repetitive content when you can just pay for a month and download everything, wait a year, and then do it again?
If these sites were smart, they'd implement a 3 month rolling backlog and then a set add-on price for accessing additional months worth of content.