My Raven Tour is running a 40 16 with a KMC Z51 chain.
It's coming up for 5000 miles and 3 years old.
Most of that mileage was done with 25kg plus of luggage on dirt tracks in the dry and on tarmac in all weathers.
The EBB has run out now. Next time the chain starts to flap I'll be taking out a link.
Hope that helps as a comparison.
Speaking to Josh at SJS on the phone yesterday he said that single speed chains have less need to stretch sideways and so last longer.
One is on the way to me with a complete new chainset for my Nomad. Hopefully I'll be updating how long that lasted from somewhere near Nepal.