Yes, there are instances of decades of legal precedent being overturned. In the case of Janus though I think it's a bit different. For one, I think the argument that being forced to pay fair share dues constitutes compelled speech is not even specious. It's, on it's face, wrong in my opinion. So Janus appears from my perspective to be more on the legislative side. This is especially so given that Gorsuch in the ruling that the thread is nominally about said that it's up to the legislature to change things.