Too much, they decided, for just the two of them. They wanted to do too much, and all at once, and an immortal lifetime was not time enough.
And so, as soon as they could afford it, Red Katrin, the original, was duplicated-with a few cosmetic alterations-in Dark Katrin and later Katrin the Fair; and nanomachines read Old Davout, blood and bone and the long strands of numbers that were his soul, and created perfect copies in Dangerous Davout, later called the Conqueror, and Davout the Silent.
Two had become six, and half a dozen, they now agreed, was about all the universe could handle for the present. The wild tangle of overlapping interests was parceled out between the three couples, each taking one of the three most noble paths to understanding. The eldest couple chose History as their domain, a part of which involved chronicling the adventures of their sibs; the second couple took Science; the third Psyche, the exploration of the human mind. Any developments, any insights, on the part of one of the sibs could be shared with the others through downloads. In the beginning they downloaded themselves almost continually, sharing their thoughts and experiences and plans in a creative frenzy. Later, as separate lives and more specialized careers developed, the downloads grew less frequent, though there were no interruptions until Dangerous Davout and Dark Katrin took their first voyage to another star. They spent over fifty years away, though to them it was less than thirty; and the downloads from Earth, pulsed over immense distances by communications lasers, were less frequent, and less frequently resorted to. The lives of the other couples, lived at what seemed speeded-up rates, were of decreasing relevance to their own existence, as if they were lives that dwelled in a half-remembered dream.