I'm probably going to get different answers from asking this, but I'm still curious

What's the best way to store figures that are more at risk from discoloring than others, like white plastic or copious amounts of white paint? There's a good chance I'm going to be downsizing my shelf space soon and some figures will have to go into storage, but I want to take steps to ensure discoloring doesn't happen.

I had my CW Superion in a box in my closet for the last few years and discovered parts of him have discolored SLIGHTLY, so I'm a bit paranoid.