Board Thread:Theories and Speculation/@comment-26636534-20150921160743/@comment-26537507-20150921173920

In the case of eyes like Madara's, the way I understand it is that you lose the eye completely, so if you had two Rinnegan eyes you would now only have one.

I think that only works if you set the technique to activate after you die. Since you only lose the eye once the technique is finished (as far as I know), it's kinda impossible to regain the eye (because you wouldn't have lost it yet).

At least that's what I think...