Countdown Dice

Roll as many times as you like, but be careful that you don't get yourself stuck! Roll the dice and swap pairs to count down rockets and gain points. But your scores do not count until you commit them. Roll as much as you want, but you must be able to count down a rocket. If you cannot count down a rocket, then you must cancel your turn and lose your progress. Can you count down lots of rockets, or will you lose your nerve?