Bring it all on, so long as it's comfortable. Fuck the rest if it gives me a wedgie . . . or, Heaven forbid, camel-toe.
This particular theory has to do directly with comfort. How do you know how to trust someone? How do you know you are comfortable with them?
By sleeping the night through, while you sleep at their side.
True comfort in your most vulnerable position. Sleep is vulnerability. None of your defenses are up, you cannot play any of your games. Your shields fall, and you become helpless.
Picture this: your first night sleeping next to anyone. Male, female, it doesn't matter. Even, your first night in a new home, in a new bed. How often do you sleep the night through, in complete and utter comfort?
I think it is a safe bet that it's rare.
However, if one can pass the whole night in complete and utter comfort, sleeping next to someone, it is safe to say that you are comfortable with that person. Perhaps it is someone you have slept next to fairly often. Perhaps someone you are meant to be with.
It doesn't matter.
You just are.