My thoughts on this since we don't know the whole story.

Customer doesn't want cameras to recorder at certain times which is fine, but do they also not want to cameras ON? This is where utilizing the schedule or power cycling the cameras is in question. Just because the camera isn't recording (utilizing the schedule) doesn't mean someone could be watching it live which may be what the customer is not wanting.

If they don't want the cameras on at all, I would get something in writing stating that continuous power cycling of the camera/s is not recommended and can cause failures to the unit which will not be covered under warranty. You may also run the risk of lens fogging, moisture buildup depending on where you live when the camera is Off due to no heat within the unit to evaporate the residual moisture.