Mine has been out of box since I got her in 2008ish? The art ponies have all held up remarkably well for me! They still looks fresh out of the box.
To be fair I AM a vampire and have blackout blinds and curtains in my room, so absolutely no sunlight is getting in!
I can’t remember where I stored her back when I was still in school and didn’t have the set up I do now, but it may have always been out of direct sunlight.