You can make selections up to five (I'd be cautious and say 15) minutes before each game and can move them confidence points to the still available confidence points amount.
Example, if I pick ND today at 35 points, I can switch the game pick at any time before that game starts, and can switch to a different confidence point, assuming I haven't assigned that amount to an already-played game.
So in other words, you can select the games as you go along, but the confidence points played already are off the board and you can select points only among the remaining unplayed confidence points.