Board Thread:Theories and Speculation/@comment-1783334-20150505045012/@comment-734582-20150505111741

Karthikkasturi wrote: The sharingan didn't need 10 years to recharge. It was the genjutsu that needed a recharge time. The recharge time was long because of how strong the user was. Hours or at worst days after using it, Danzo could use it again (he used it on mifune during the Gokage summit and was about to use it on Obito during his fight with Sasuke). Only a sufficiently powerful user can make it recharge fast enough.