Cath Lab Trays

I apologize if this is a subject that has been addressed, but I have been unable to find any concrete data on 'How long before an unused sterile tray needs to be disguarded?' (both wet trays and dry trays) There was a short forum in the Cath Lab Digest a couple of years ago. People commented and said what they do at their own hospitals, but nobody made reference to any published data on the subject. AORN guidelines state that trays should be made up just prior to procedure and should not be covered. Being a different entity, I would think the Cath Lab would have some different considerations. Currently, we disguard wet trays after 8 hours and dry trays after 24. But as I sat down to write a formal policy I was unable to support these numbers. I would like to hear your comments, but especially love to hear if anyone has any references. THX