My RMR dual has been through years of abuse. Rain, snow, freezing cold, heat, mud. Then last year I slid down a drainage tube into thigh high muddy water (Run-n-Gun event). I dropped the gun hot, got DQ'd. It had worked for about 8 shots. I noticed it stopped working after that drop. Trijicon fixed it in about a week. I bought an SRO after that so I still think they are damn tough sights.
I haven't had any multiple dots or obscured lenses. There's a hole in the side of the sight. Blow through it and it cleans everything well enough to use.
I had an issue one time in the rain when I was taking a night fighter.... basically the dot no longer looked well like a dot. it was all fuzzy and cloudy..... there was still enough in the center to tell where the dot should be.... but it made me question whether I should go for the acro next