Yes, our sockets have an autoretracting dust cover. Cables or couplers do not. I don't know if dust would be a problem or not. I would suspect it would not be that big of an issue. The contact on the autoretracting dust cover during insertion might even serve to clean off accumulated dust.

I suppose that the intensity of the light would decrease according to the inverse square law, but I could be very wrong. I guess it depends on the angle of the light exiting the cable tip. I do know that the cable need not be inserted "100%" to produce sound. I have had it as far as 1/4" out and it still worked.

Regarding the life of the RCA connector. You could try what others have suggested doing. Run the coax signal over the mic in line. I am going to make a custom docking connector for my unit with a short female video cable connected to the mic in lines to avoid using the RCA connector completely.

Stu