I wipe things down with a damp sponge/soft cloth
(water only) and keep them out of the sun; no
yellowing problems here. Important equipment gets
wrapped in plastic before storage.
There was one exception. Floid mentioned (in the
related thread) that skin oils are a likely
culprit, and he is right. Years ago I had an
old C128 that yellowed right behind the spacebar,
where my (somewhat young) palms rested on the
keyboard. The rest of the case is still beige.
