In a large bowl, dissolve yeast in warm water. Add milk, 1/2 cup sugar, eggs, butter, salt, and 3 cups flour; beat on medium speed until smooth. Stir in enough remaining flour to form a soft dough.

Turn dough onto a floured surface; knead until smooth and elastic, 6-8 minutes. Place in a greased bowl, turning once to grease the top. Cover; let rise in a warm place until doubled, about 1 hour.

Mix cinnamon and remaining 1/2 cup sugar.

Punch down dough. Turn onto a lightly floured surface; divide in half. Roll each portion into an 18x8-in. rectangle; sprinkle each with about 1/4 cup cinnamon sugar to within 1/2 in. of edges. Roll up jelly-roll style, starting with a short side; pinch seam to seal. Place in 2 greased 9x5-in. loaf pans, seam side down.

Cover with kitchen towels; let rise in a warm place until doubled, about 1-1/2 hours. Preheat oven to 350°.

Bake until golden brown, 30-35 minutes. Remove from pans to wire racks to cool.