"They keep us alive. It's not always a different face. My brother has managed to match his last few with some concentration. And some are chosen. Mine usually happen under traumatic conditions so there's no time to concentrate."

He's been just hovering thus far, and he looks for some surface that he can sit on that might be able to support his weight. If nothing else so he can get over this abysmal supervisory feeling.

"Thirteen simply because the regenerative materials start to degrade. Do remember, each of these regenerations ends up a personality living in the back of our mind. Each regeneration is imprinted on our time ship. So if we call upon more than thirteen, that's more personalities lurking. We have very vast intellects, but very delicately structured minds. It's a bit much emotional weight to bear for synapses meant for logistics."