Thinking about putting truglos trit/fiber combos on one of my firearms.. My local ffl seems to think they are amazing (because of the day/night benefit vs just "night"sights.) Curious for anyone who owns them.... Since the fiber optic tube is, in essence, "OPEN" on top.. Does all kinds of crap, dust,lint,chemical, oil,etc - get "inside" there??? Seems like all sorts of crud would get in and ruin them?