Stir together first 6 ingredients in a heavy skillet over low heat, stirring until butter melts and sugar dissolves. Add pecan halves, tossing to coat. Spread pecans in a single layer in an aluminum foil-lined 15- x 10-inch jellyroll pan.
Bake at 250° for 1 hour, stirring every 15 minutes. Remove nuts from oven, and transfer to a large piece of aluminum foil. Separate nuts with a fork, and cool completely. Store nuts in an airtight container for up to 5 days at room temperature or 1 month in freezer. If frozen, bring to room temperature before serving. If nuts become sticky, bake on an aluminum foil-lined pan at 250° for 20 minutes or until crisp.