Board Thread:Wiki Discussions/@comment-24891350-20140505041253/@comment-2005101-20140505054301

It hasn't actually been confirmed, but the power of Hashirama's cells are the most plausible explanation at this point. If they could reduce Kotoamatsukami's cool down period from a decade to a single day, then slowing down or preventing the Mangekyō Sharingan's deteriorating "light" is quite likely.