Combine 6 cups milk and salt in a large, heavy saucepan; cook over medium-high heat just until milk starts to boil. Gradually whisk in grits and butter. Reduce heat; simmer, uncovered, 20 to 25 minutes or until thick, stirring often.
Preheat oven to 350°. Remove grits from heat; add remaining 2 cups milk, stirring to cool grits mixture. Stir in eggs, herbs, and 1 cup cheese. Pour grits mixture into a lightly greased 15" x 10" baking dish; top with remaining 1 cup cheese. Bake, uncovered, at 350° for 45 minutes or until bubbly. Sprinkle crumbled bacon on top of casserole; serve immediately.