I have the tractor you described it is stored both inside and outside. Guess I will fess up and say more outside however..... I have not had the instrument cluster fog up but a couple of times, this was due to nothing more than a temperature variation ( early morning moisture ).
The dash is made of plastic and continues down to the floorboard "as a makeshift kick panel". There has been some fade but I keep the plastic oiled - used motor oil on a rag and wipe it down occasionally. Plastic parts seem to dry out over the years, become chalky, and loose there pigment. I used to own a truck that had the flashy plastic overlay on the bumper and with enough oil applications it seemed to soak up and revitalize the plastic.
Plastic (or likes of it) looks shabby to me and; it is everywhere.....new cars filled with it, tractor panels, cups, etc. What happened over the last 30years. Read somewhere you can make a gun out of the stuff now!
I thought that using plastic would 'lower manufacturing cost' but over the years..... All tractor/automobile Mfgr's seem to be incorporating it everywhere and the cost of the product is not being reflected to the consumer. Sorry about the rant about the plastic- got on a roll...