Getting back to the question that was asked at the beginning of this thread...I personally think that it is important to keep the visual path as clean and unimpeded as possible...

I wouldn't want anything to impede the function of the condensors...I am not anal about this...just cognizant of the degradation that can occur.

I am thankful that I haven't dropped or scratched one of my condensors since I began using a condensor enlarger...

On a separate note, while I can not say that every condensor system is the same as those in my enlarger, the manufacturer clearly states that the purpose of the condensor set is to focus the collimated light at the nodal point of the enlarging lens. In my enlarger I have a number of different focal length condensors that are specific to different formats.