Board Thread:Naruto Discussions/@comment-4682609-20140806081616/@comment-4271790-20140806093338

He said it "might expire." Unless that was a translation error, considering everything we've seen so far, that means it could go blind if overused. But it can be temporary, given the method used for Obito to hand over his Sharingan to Kakashi... then again, Kakashi said he and Obito will see the future together... Meh...