rebills don't occur because the user is active and enjoying it... for every 20 members who are rebilling cause they forgot there is more like one that is recurring puprosely.
I say this not just as a pps program operator but as one of the owner and operator of several of the original "real" solo girl live cam interactive members sites. (back in 98... no longer live. models are too much work)
if a paysite simply wanted to make sure that only active users are rebilling they could easily script it so that on login if you have expired they renew you for another month.