It really depends on the bitrate as to which the video is recorded at, each camera on it's various settings would record at different bit rates.
For example.
GoPro Hero 3 Black at 1080p and 60fps records 17min25sec at 3.94GB.
So each 32GB card could hold 2 hours and 20 mins.
Taking into account that it will take around 60 hours to complete, the GoPro would need 27 cards
Contour ROAM at 960p and 30fps (set to the higher bitrate setting) records 51min33sec at 3.94GB.
So each 32GB card could hold 6 hours and 50 mins.
Taking into account that it will take around 60 hours to complete, the Contour would need 9 cards.
The calculations are an estimate and times are taken from recordings from my journeys in the day time. The bitrate at which the videos are recorded at varies, not only from camera to camera and mode to mode but also depending on the light conditions and colours. White takes up less memory to record than black.
If you want to try and get a clearer answer, then test how long you can record for with your camera, preferably in daylight and moving. That way you can work out roughly how many cards you will require by how big the file is and how long it is.