Letting the batter sit before baking will cause the sprinkles to begin to melt and the colors to bleed more. It is best to get them in the oven right away! If you can only bake one pan at a time, divide the batter into two bowl and stir in the 2 T of sprinkles just before pouring in pan and baking. Also note, each sprinkle brand dissolves at a different rate. I'm working with Betty Crocker brand.