[Formendacil]

Without thinking long on the matter, it seems to me rather strange to suggest that Sauro would have retained for himself Rings that expressed turned one into a Wraith if his purpose were re-embodiment. Stretching his life into longevity would hardly be necessary when, as a Maia, he'd already cheated death and the destruction of his body.

No, it seems to me that Sauron wanted the 3 of Seven, and the Nine for reasons other than re-incorporating, a process which, in any case, I think only the One would have helped him with--not because it was a Ring, but because it was a Ring into which he had imbued so much of his power. It seems to me more that he wanted the Seven and the Nine for other reasons. Whatever other powers they might have, I'm not sure I'd want to speculate, but it might not have been for their powers at all, but simply so that, once he had the One again--or in case he did not recover it--he would not have other people running around with powerful Rings. In other words, not in order to use them, but to prevent other from using them.

Hmm... now I'm wondering... let's imagine that Gandalf or Saruman had the One Ring and was set on becoming the new Ringlord: would Sauron's possession of the Seven and Nine have been a defence against the Ringlord, or would they have weakened him against the Ringlord--as the Seven and Nine were meant to bend others to his will when he had the One?