The fact that I won't call the police is irrelevant. "It's a crime, but you'll never get caught" is not, to me, the least bit reassuring.

I don't see why, in a lasting relationship, you can't have lasting consent. To take a fairly trivial example, I am in the habit of patting my partner on the backside when I come home from work. I do not ask for her consent each day. She has given enduring consent; she can withdraw it at any time, but until she does, it continues. As with the opposite case, I am not reassured by "but she will never call the police abut it".