Storing the spare tires that come with new engines seems to be a losing battle against time. If not already in a sealed plastic bag, i.e. stapled plastic bag, I put them in small zip lock baggies. Never seems to fail when I need to retrieve one, the pack seems as dry rotted as the original mounted tires. I keep them out of sunlight or UV sources (cardboard box with lid) and in a human friendly environment as far as temperature and humidity. Judging by the purchase date of the engines, the majority seem to dry rot anytime after six years of storage. Some don't show signs of rot (i.e. the shiny vinyl looking ones) and seem to endure while others, particularly the dull looking ones, rot before they are needed. I know rubber and some plastics "gas off" and is inherent to drying out. I was just wondering if any of you have any tricks to keeping them "fresh".