Some years back, I did such a session. It was only for 24 hours. But, it was intense and definitely one of the most memorable sessions I was involved in. One of my dom friends joined me in putting it together. We decided to be equipped for everything but let it go with the chemistry and let it go in the natural direction. As it came to be, sleep deprivation and a stockholm syndrome of sorts were strong elements. Half way into the sub and I were so in the headspace, that my fellow dom hung back and facilitated the emotional wave we were riding. I'd have to wonder about doing something to deep without a second dom. But, it was a once in a life time. The sub and I talked a short time later about the session. It has taken us both a few days to get our heads back to earth. If you ever venture into this, I'd love to know how it goes.