The nearest expiration date for PJM Western Hub Peak Calendar-Month Real-Time LMP Futures (Feb 2018) is Jan 31, 2018.
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 PJM Western Hub Peak Calendar-Month Real-Time LMP Futures (Feb 2018) before Jan 31, 2018.