Interesting comment Vince made in the "Campfire" thread, I think it was, about the volatile substance that makes these tyres soft diffusing off over time. Could also be some additional cross-linking taking place, but whatever it is, rubber obviously has a finite life span and to lengthen it, as in the storage of rubber parts, some type of barrier coating on them, or possibly vacuum packing, might be the answer. I asked that question (rubber storage) under Tech tips, and the answers were, from Matt, wrapping the parts in greasy paper, and from Dew, spraying with silicon spray - either might work. I suppose with tyres you would normally expect them to wear out before they crack and get hard, but maybe that isn't always the case. If not, is there a way to extend their life while they are on the bike, in storage say?