In a large bowl cream the butter and sugars with an electric mixer until fluffy. Add the eggs and vanilla and mix well. In a separate bowl stir the flour and baking soda together and add the mixture to the batter. Stir in the ground pecans. Form the dough into rolls on wax paper and refrigerate for at least 12 hours. Slice thin and place on ungreased cookie sheets. Bake at 350 degrees for 8 to 10 minutes.