It leads into all other sorts of questions, like whether they have an MO and stick to it, so many maidens get trapped in many towers, and many princes get trapped into laboring for the ogre, or if the villains jump from fairy tale to fairy tale.
And noting that over time, a number of villains in tales must be cat's paws or at best front-men for the villains actually pulling the strings. (At least for this one. A society consisting of all sorts of wicked stepmothers and sisters from all ranks in life from peasant to queen, plus at least as many evil mothers, oppressive fathers and brothers, random tyrannical kings, ogres, trolls, giants, dwarves, fairies, and many, many, many more would probably be comic and certainly would not fit here.)
And I finally concluded that it would probably be about a century. Not because Sleeping Beauty went to sleep at the beginning -- she was one of the successful ones pre-warping -- but because it would give them time enough to have a starting point and still leave a trail of ruin behind. Also let me decree that various heroes and heroines died of old age with their fairy tales still ruined.
And then I just have to decide why, in a world where escaping a kingdom is always easy walking distance, they don't just run away when a tyrannical king demands labors.