One of the benefits of pt/pd printing is that the metal used is very stable. So UV light should not be a problem. I would be more worried about possible side effects on the paper stock from ingredients in the spray than I would about UV light exposure. One interesting thing about platinum prints is that the platinum DOES act as a chemical catalyst (as anyone who has paid for a replacement catalytic converter on their car will know), and it will cause chemical reactions in the papers that are in contact with the image, and form a ghost image. I have several 100 year old prints that have been stored next to platinum images and show a ghost image on the back side of the prints. Here is an online discussion of the phenomenon:
http://www.alternativephotography.com/articles/art063.html
Cool, huh? So if you use a nice quality separator paper for your prints, you will end up with an additional print eventually! This could really screw up the whole edition numbering thing. Maybe we could have the current recto edition, and a 50 year delayed release of the mirror image verso edition!