Sounds like you have the experience. I runt he Marathon slicks, and don't expect too much from them. I was more under the impresion that 5000 miles was the limit on most touring tires, not to say one won't get more, but whatever the service limit is, it isn't going to lead to good comparisons if the trip exceeds the tire's actual planed life. Anyone know what that design life is expected to be? Is there an industry norm.

It's also almost impossible to compare terrain. Just composion of the road surface or surface treatments, the use of glass, can lead to completely different results. I've never travelled those desert areas with thorns, but I doubt the experience is comparable to my stomping grounds. One instance where the more widely travelled one is, the less comparable the results.