I didn't go back to campaign since I claimed all 2250 rewards from prize board, as there are not really large benefits aside from testing, especially the impact of currency, therefore I could suggest a bit situation to refresh the prize board on the campaign:
-the board will be refreshed after 3 days of cleaning prize board on each level, during the time between emptying prize board and being refreshed, no rewards will be given but it will never block the player to replay the level.
-When prize boards are refreshed, all cards shown below the boss car next to each chapter are also refreshed.
-prize board will not include prize cars.
Should everyone have suggestions, please leave comments sine this is my first time to give suggestions.