Thanks for your reply. I guess I was thinking in terms of condensation and the like inside the light, or just leaving it open to the air. I know they're petrol-proof but if an thinking of some form of oxidation from water itself?
I doubt it, I've had de-domed lights out in all weather and condensation has never affected them, I think any water/condensation that would be there would be evaporated when the light is turned on (that's not a scientific explanation, just my opinion!) but even my de domed triples all work fine, so if they were going to fail I think they would have by now, but if they do just stick a new emitter in! Aha