I've had the 505 for about 16 months and have read the posts about sun fade (also
this one) on various devices. I understood from the various threads and posters that it was due to a "bad batch" of screens by LG which were used on a variety of brands of e-ink devices and not on just one brand.
I've never had the sun fade problem on my screen. I read outside everyday in nice weather. The only thing I notice is that the leather cover gets very warm. It is usually 90 degrees plus outside and I sit with my back to the sun (but the sun is on the screen of my Reader).
It seems to not be a brand problem but which batch of the e-ink screens were used on your device problem.