I dont know how long those 40" X-terrains last but for $650 ea. they had better last at least 40-50k. The tsl's do not wear as fast as the i-rocks because the i-rocks are softer and more rounded on top. Tsl's are good, the X-terrains did not do so well in washington mud or the oregon sand, but on the rocks and in the snow they were really good.
