Hi: I'm new at swing trading the mini s&p's. I'm long the March contract. I know tomorrow that June becomes the front month. Is it better to sell my March contract and buy the June today or is it best to do it the day that June actually becomes the front month? I'm talking in terms of the bid/ask spread. Right now the bid/ask spread on the June is usually .75. The March is usually .25. Just trying to minimize my slippage. Thanks for any help.