Tyre wear mileage was as follows:
Tourance - 11000 miles (99% tarmac Europe to Uzbekistan, Korea to Alaska) Rear tyre bald, front with a few thousand miles left)
TKC - 7300 miles (50% offroad Uzbek/Krygy/Kazak/Mongolia/Russia) Rear tyre bald, front tyre badly saw-toothed
K750 front - 5300miles (Canada/America) 50% worn
K750 rear - 3300 miles (sharp Alaska/Canada roads) bald
K750 rear - 2000 miles (40% worn)

Original chain & sprockets - 15000 miles- chain knackered, rear sprocket good (includes 6000 miles in the UK before departure)
Replacement chain (DID Oring) Renthal sprockets - 12000 miles - chain good, rear alloy sprocket badly worn

As Scott says, the way to go is with a good quality Oring chain, and the original steel sprockets.

Hope that helps