Board Thread:Naruto Discussions/@comment-24373005-20140811055011/@comment-5407586-20140812082020

The Mangekyo Sharingan is unique in that the more it is used, the faster its owner loses the light. Itachi rarely used it for almost 10 years, spamming its techniques only in the final fight against Sasuke. Same for Shisui, whose Kotoamatsukami couldn't be used more than once in a decade without Hashirama's cells. Obito may have not abused Kamui in the 20 years he had the Mangekyo Sharingan. It seems that Susanoo is the Mangekyo jutsu that leads to blindness far quicker than any other power, something Tobi told to Sasuke when the latter decided to trasplant Itachi's eyes: "You used Susanoo way too much ."