Consent is a very complicated thing.
My guidelines for consent have always been

Consent beforehand
Consent during and before specific acts
Consent to stop whenever you want

It's why I'm contact neutral for zoo, cuz I feel like 2 can be hard to gauge.
But I was thinking about consensual somnophilia. In the past a sexual partner and I talked about using each other in our sleep, and how if we did we'd give consent the night before. (Sadly it never ended up happening :( )
I 100% believe this to be true consent, as I'm telling someone I consent to them using me while I'm asleep.
But at the same time, this doesn't satisfy points 2 or 3 of the basis I've been using for "proper consent".
Makes me rethink my contact stance for zoo a bit.
Again, consent is complex.