That’s a tricky one. Normally, I do a one year PQ to account for seasonal variations and it sounds like you’re already planning for that. However, your company’s plan to shut down utilities during the night definitely add an extra challenge into your system. Since it sounds like you’re concerned, I would suggest a reduced level of monitoring during the night conditions or maybe first thing in the morning before the utilities come back on line. Your primary objective should be to show that the water you’re using in your process is of appropriate quality. That said, I would think that you would also want to know how the turning on and off of the utilities affects your water system.
Without knowing the design of your system, that’s probably the best advice I can give you right now. Whatever you decide, just make sure that it is spelled out in your validation plan/protocol with your rationale as to why you picked the testing.