As long as you keep the O rings in good shape, most of the lights are fairly waterproof.. I use my P7 in a light rain today with no issues.. Not sure how it would handle a downpour.. It seems that leds are much more bulletproof than other types of lights.. I have led flashlights that go back 5 years + and they are still going strong, which is one of the reasons I love the P7..

My Arc HID started to look dim after about 18 months of use and they recommend getting the bulb replaced every 2-3 years for maintenance, but of course it is not cheap or user replaceable..