I think the desire becomes a need when you can't do anything until you have fulfilled the need. Just because you won't physically/naturally die from it, doesn't mean it won't fuck you up mentally if you don't have/do it, so I would still consider it a need. I know this is true for my partner, when he gets a craving for...something, he has to have it then or he can't bring himself to focus on anything else. As for me, I feel like I NEED to feel pain sometimes or else I'll go mentally insane and just totally break down. So that's kind of a temporary need, as for long-term, I know that I need him to dominate me and my life or else I wouldn't be able to function by myself at this point. Definitely more of a need than a desire.