Since I have gone to the Darkside, of course the rear tire will last a long time. I installed it on April 2008 and have over 25,000 miles on it. I still have quite a bit of tread left and could probably go another 10,000 miles or more. But here is my question. Does the rubber brake down over the years and become more brittle? My tire doesn't show any signs of cracking but have been thinking about replacing it even though there is plenty of tread left but i'm concerned about the age of the tire. Any thoughts on this matter?