wsippel said:In the epilogue, there's an elevator, followed by a very long, curved corridor. The navigation room at the end of that corridor is the point of no return.
Technically, the room AFTER that navigation room you mention is the point of no return (and an extremely obvious one at that, considering what happens when you enter.)
You can get that far, save, but decide to backtrack all you want. (Or reload if you enter the following room and feel unready to continue.)