The thing with Nick is that he really doesn't like fighting people; either for money or just to fight. Imagine having a job you dreaded going to everyday, but you go because you need to support yourself, and then all of a sudden you run into a huge payday, would you want to go back to that job you despise so much? I know he has said that he would rather work a normal job than fight, but when he runs low on money, he may come back, who knows.
With Nate, I think its different; I think he likes to fight. I don't see him ever being champion, but his skillset is very high and he needs to start using those skills to make a living otherwise his attraction to the fans wont be as strong. He just needs to call and tell them he wants to fight asap, put aside the b.s., win a few fights, and then he can renegotiate his contract.