Board Thread:Naruto Discussions/@comment-4682609-20140806081616/@comment-5909893-20140808020655

Just saying, in the Narutoverse, although it's known that the Mangekyo Sharingan can cause blindness with overuse, but in Kakashi and Obito it's been sort of downplayed. I mean, Obito began using his Mangekyo long before Itachi did, and seriously, he's never mentioned going blind or his vision worsening. So really according to that I think when Obito said 'It might expire' it was just a simple afterthought, considering the context. He was like "After all you are Kakashi of the Sharingan, aren't you?" so if it just goes away that will just go back on everything he said.