Well, the tongue is not really an indicator of when to end the fast. For most people, the tongue will remain white throughout thier fast, even longer fasts.
I take it that you have set a goal for your fast. When you reach that day, see how you feel. If you feel good about continuing, do so. If you feel good that you have accomplished your goal, then consider that a successful fast, which it is. Most of all, enjoy the experience.