Marilee Stone's issue was never dealt with, as far as trying to get her any help, but she was a nymphomaniac. She made Lucy seem chaste. I don't think it even occurred it Marilee that there's supposed to be a spiritual aspect to sex.
JR had a genuine problem with illicit sex. I don't know if he was capable of remaining faithful to any wife for a substantial length of time. He always wanted what he did not have. There was a time when he told Mandy that all his life all he'd been concerned about was "the chase" and after he'd gotten what wanted he couldn't wait to get away. Mandy looked frightened, like she expected him to say he was no longer interested in her but he said to her: "Darling, what I'm saying to you is, it's different with you. I want you now more than ever. I cant't tell you what a wonderful feeling that is."
It seemed like he'd finally gotten a handle on his problem and that Mandy brought about that change he needed, but then the show just dropped that storyline. They would be on the verge of showing some character development, but they couldn't commit to it. It was like that in season 11 with Cliff: he told Miss Ellie that day in the park that he'd finally learned his lesson - that revenge is pointless. He said the only thing he wished is that Pam could be there to finally see her brother learn his lesson. Cliff became a decent man for once and it was good because it gave the show something new. It was a progression in the story. Again, they just couldn't commit to it, they'd get hesitant and slide right back into the same old pattern. An audience will only watch people doing the same things over and over for so long before they get tired of it.