I fitted PR4 Trails for the first time, and have done 3000+ miles on so far. 1,700 of those was on Motorways with heavy panniers. No squaring off, but I would estimate that the rear will last around 4,500 miles. That, to me - is good considering the cornering grip compared to a 6000m-range Tourance (German) or 4,500-5,000m Tourance (Chinese).
Great tyres in the Alps twisties, and I doubt I would go back to a Tourance-type tyre. Some people want absolute longevity, which is fine too.
Some people expect ultimate grip AND ultimate longevity................. I don't think that is realistic
Al