I've just tested several 5 minute high intensity orange lightsticks, dated 2005, 2008 and 2009.
All of them were still VERY bright (but, I imagine, not quite as bright as in date ones) and all gave a good, useable light for 40 minutes each!
Think I might hunt down some out of date stock on eBay
good to know, I've got to be honest I didn't even realise they had an expiry date on them! something to bare in mind when buying to ensure you get the most for your money!
One warning , we had a batch of out of date cyalume lights sticks , 6" yellow 12 hr and they had a bad habbit of bursting at the base after 8-9 hours as the start to loose the brightest of the light , they were just about a month out , but be wary , it could have been a bad batch ..........
Be Prepared.
Plan like its the last loaf on the shop shelves.
Plan like its the last beer in the fridge.