I'm on my second set of 697's. The first set I replaced at 65,000 kms - but only because I was setting off on a 16,000 km trip across the Savannah Way and Gibb River Road plus the Tanami Road.
I could still have got another 10,000 kms from the first set on bitumen, but I won't set off on a trip with worn tyres.
Towing - especially something heavy - will always wear the rear tyres heavily. I got mine rotated part way through the trip - there were not many options...
I'd go with them again - unless someone else has the brains to make a good tyre in LT265/60R18.
Cheers
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