My touch up paint does not show. No one notices it but me because I remember every spot I've ever touched up (maybe 4 small chips since I've owned the car), and even if I point it out to friends they can barely tell anything even happened. Most of them say, "Are you sure that's the right spot?"
I understand each of us will defend to the death our choice, especially since you spent so much money on yours. And when I replace the bumper with a euro bumper one day, maybe I will clear bra it. I think the majority of people who have claimed their bras yellowed have had it for much longer than a year, but I'd have to do research on the topic to find those posts.
The truth is, the bras can and do yellow. Whether it will happen sooner or later is up to you.
'11 BMW E92 ///M3 - ZCP and DCT
'13 Toyota Tundra - 4x4 Platinum CrewMax, 5.7l iForce V8