The nearest expiration date for MISO Minnesota Hub Peak Calendar-Month LMP 5 MW Futures (Jun 2013) is Jun 29, 2013.
The best time to sell a futures contract is when you've already made money on the investment, but still have plenty of time left before the expiration date. Thus, a good option would be to sell MISO Minnesota Hub Peak Calendar-Month LMP 5 MW Futures (Jun 2013) before Jun 29, 2013.