Board Thread:Naruto Discussions/@comment-25691159-20200529162803/@comment-25691159-20200530201627

They stopped spreading simply because they burned up, that’s all (or it’s just a technical oversight, the flames didn’t last 7 days either way). If the author calls them eternal then they are until there is a legit way to disprove that, and if the flames burned for 7 days it would have been referenced in the manga. The databook already contradicted the manga in different ways, as it implied Amaterasu was an ability that could be learned by any Mangekyō user rather than being an innate power, or it only being close ranger jutsu when it was seen being used in much greater distances. The databook is not a gospel, manga is, and if the manga says that they are inextinguishable, then they are.

Also the 7 things itself is illogical. Since Amaterasu is shown to be spreading over anything it touches, are the flames are supposed to magically vanish after the seventh day passes or what?