This is among the most ambiguous questions I've read in quite a while. I'm a salary employee, so I can't really suggest freelance rates, but you've got to break some things down. What genre is this? Narrative and documentary projects aren't going to take the same amount of time to complete. How long do you anticipate doing the edit? Can you break down your rate into editing costs X, color costs Y, audio costs Z.
If this is going to take a quarter of your year make sure you'll be getting a quarter of the annual income you expect.
Is the client expecting this on a certain timetable? If it can be a back burner project and you can take other single day projects along the way you may be able to improve your rate.
Are you going to need new hardware for the task? Add the cost of storage into your rate. Do you need new audio or video monitors to properly color correct or mix the project? Another cost to add. Audio mixing or color correction surfaces?