Pour boiling water into a very large bowl. Add the tea bags. Let steep for 5 minutes. Remove and discard tea bags. Stir in sugar and cinnamon until sugar is dissolved. Stir in pineapple juice, cranberry juice, and lime juice. Remove 3 cups of the mixture. Cover and chill the remaining mixture for at least 4 hours or up to 3 days.
Pour the 3 cups tea mixture into two clean ice cube trays, adding kumquat slices, if desired. Cover and freeze until firm.
To serve, divide prepared ice cubes among glasses. Add chilled tea mixture. If desired, garnish with fruit and/or mint. Makes 8 to 10 (about 8-ounce) servings.