Well I haven't been trooping long enough, or out in the direct sunlight enough to find out how long it takes for the armor to yellow, year, two, three? Maybe someone can answer that question. If it's any consolation last week I was trooping and people were looking at me like I just pulled the armor out of the brown box, someone finally said "Dude your armor is too clean". I took it as a compliment but I don't think it was meant to be.
Simply put, I've had 3M polish or Miguires on my armor since day one and to be honest I'm more concerned about the heavy dents and scratches I've put in it bumping into things. At this point I'd be happy not to crack the thing by years end
Let us know what polish works for you.