There is no line. Everything gets evaluated on a case-by-case basis... and even on a class-by-class basis.
At one end of the spectrum, I've written a simple 4-page almost-static doctor's office site that uses Redux to manage page titles and the logic around office hours and whether the office is currently open or closed. It's very very simple code and I could have easily written it without Redux... but as another user said, there's very little overhead and if you like it and understand it then use it.
At the other end, I'm currently working on a much larger digital asset management application and I have a component that allows the user to visually arrange the layout. I chose to not use Redux for some state (cursor position, drag states, hit testing, etc) because it felt like overkill -- specifically a lot of ceremony to create an action, figure out how I want to store the data, add cases to a reducer, add more selectors, passing values in mapStateToProps, etc. instead of just assigning to a local variable and being done.