This is only my second year with them. I dont notice any sun damage. There are many youtube homesteaders who've used them longer. You might get a better answer, there. There are also greenstalk groups you could ask on Facebook, maybe MeWe. Maybe even on the sister sites to BYC.A question for the Green Stalk growers...
How well does the plastic of the Green Stalk hold up to sunshine? How many years of service do you get before they get brittle?
I also have many plastic pots that I've used outside for a dozen years with no issues.