Vicekid is 100% correct. In this type of business models come and go all the time. We do our best to try to keep them going for a while, but we can't force them to do more shoots with us.
Some end up at other studios that offer them very large amounts of money. Some just never do it again, they try it and they feel its not for them. Some we don't bring back because either they have mental issues and cause lots of problems and drama off camera. Some just can't film porn and its not for them and we don't have them back. Some there parents and friends find out and they get into a lot of trouble. Some go to jail, while others get in trouble with there girlfriends and the drama starts.
We also look at what members respond too. If a member really likes a model, we will do our best to bring that model back. If the members are not crazy about a certain model, we don't bring them back. Some guys come here, I think are cute, but they just don't have any "spark" or "pizazz!" So they are no memorable...so they just fade away.
So there are lots of variables why you don't see certain models back and why others return.
-David