Several possibilities as to why it stopped --all on the husband, I'm guessing. (1) He liked the early sessions because they seemed relatively tame, but as you got more intense, it set off alarm bells in his brain. (2) He figured this was a one-time thing, and then maybe a passing fad, but as you continued to fuck his wife, he was afraid she was enjoying it far too much, which put their marriage in jeopardy. (3) He was never truly on board from the beginning and only went along because his wife was pushing for it. It just got too intense for him.
It's possible this situation has ended for you, based on the three possibilities I've listed above. However, there could be a cooling-off period where they're willing to pick up again. If that happens, I'd suggest not escalating things to an intense level.
