Here is one thing I never quite understood about the last jutsu Nagato was to activate before he died:
I got suspicious when Tobi became angry with Nagato because he used his Rinne Tensei on Konoha and not for him (whoever "him" might be) ([URL]http://www.mangareader.net/93-458-17/naruto/chapter-453.html[\URL]). Actually, there is little we know about that technique. We know that it can be used in order to revive the dead ([URL]http://www.mangareader.net/93-454-1/naruto/chapter-449.html[\URL]). We also know that it takes a huge amount of chakra (yet I never actually got that part since he used it after he had attacked Konoha, summoned tons of creatures, fought Naruto, levelled Konoha by using a very strong Shinra Tensei and activated Chibaku Tensei before he activated this jutsu).
As Neji once said: "Such a convenient jutsu (to revive the dead without any drawbacks) can't possibly exist" ([URL]http://www.mangareader.net/93-284-3/naruto/chapter-279.html[\URL]). And if it did, it would leavy many questions about the Rinne Tensei unanswered, for instance: Why didn't Nagato brink Yahiko back, or at least Deidara, the "two zombies" (Hidan and Kakuzu), or Sasori? There must be a reason to this, and it is hardly convincing that it is because it takes a lot of chakra. Many jutsus do.
And last but not least: If it had been possible to use Rinne Tensei as often as you need it, why not make the Edo-Tensei-Nagato reuse it in order to revive - let's say - Orochimaru? You don't even need DNA-samples.
That's why I am convinced it is not possible to use this jutsu more than once. It is a once-in-a-lifetime-technique, and he used it for his fellow child of prophecy?