I also have a Mercury Vapor (?) light on the front of the house with a Southern exposure.....the direction the heavy weather comes from. It pumps out a lot of light......lights up my dark street. It too has a ambient light sensor. I save the original box & 1 year warranty. I've gotten 2-3 new ones for those that puked.
There's something in the sensor circuitry that is sensitive to moisture, me thinks.
No flckering/fading, just stops working.