I use PLA Plus and I never have issues with exposure to the elements. If PLA is left in direct sunlight in a car it can get hot enough to get soft and distort but I keep my OpenPPG in the trunk so that hasn’t been an issue. And if a part ever did wear or distort… hey, I printed it in the first place so I can just print another one.
Yes, PETG has its advantages but regardless of which material you print with the layer lines will always create a weak direction and therefore the changes above are necessary for optimal strength. I’ve worked with PETG with my Prusa and have been satisfied with the results but I don’t have any red
Also, it’s not exactly prototyping if I never intend to make it with a mold later. FDM printing has become more and more a manufacturing process and not strictly for prototypes. All of the plastic parts on the Prusa are 3D printed but that doesn’t make them prototype parts. What it does do is give them the ability to constantly make small improvements to their product that with other processes could cost thousands of dollars to change.
Enjoy your Prusa and I hope you have good luck with it… have you ordered some red PETG to use with it?