Originally Posted by Shino'sDad
Edo Tensei revives a Ninja in their prime. It just so happens that Ninja rarely die of old age, and usually die in Battle, and mostly when they are in their prime. If the 3rd Hokage hadn't sealed himself away in the death god, and had been revived by Kabuto, he would have definitely come back much younger than he was.
The only one that doesn't fit is Nagato, but I think that was mostly plot point.
It was never mentioned anywhere that Edo Tensei revives a ninja in their prime. What about Chiyo? I doubt she was at her prime at the age she was, it was exactly the age she died at, just like everyone else. Nagato was also at the age he died, he just absorbed a lot of chakra via his Rinnegan techniques and revitalized, sort of. The only one who came back younger than at the time of his death was Madara. It could indeed be Kabuto's doing, but I really wonder about it. It seemed more like he applied some of Yamato in him, similarly as he did with the Zetsu clones, plus he implanted a Rinnegan copy in his eye, like he did with the revived Jinchuuriki. Which brings up another question - how come Rinnegan can be multiplied like that, but not Sharingan. I guess it may never be explained though.