Many PIR sensors are programmable by switching on/off/on etc. So a power cut can change the programming, also water can be a problem, I drilled a hole in bottom of mine, after checking was was inside, so water could drain out. It was well sealed at bottom so PIR filled with water.
I have moved from PIR controlled to smart switch controlled, mainly as the PIR would switch it off at most inappropriate moment, and when out I normally take my phone, so easy to turn on when required. The LED uses that little power having a timer is often better, but I do switch off to stop light pollution, on at 9 pm off at 10:30 pm on at 6:30 off at 7 am for milkman.
Better quality have some adjustment on light levels, time, and sensitivity, but as said when using 300 watt quartz (yes I know 150 watt is legal limit but we had 300 watt tubes at work) having it only one when required made sense, but at 15 watt, only problem is light pollution. And I do not want visitors at midnight, so see no reason to make an intruders life easy, better if they can't see what they are doing. Security lights need to be outside human visual spectrum so only the camera sees what is going on. Anyway more fun that way.