Please tell us how to get 12K from a set of tyres
I don't really know, maybe I'm smoother than most, I tend not to break or accelerate very hard, but it's not like I never do it. Most of my riding is not done on city streets, maybe 10% of the mileage, 30-40% highway at moderate to high speeds and the rest on secondary roads at reasonable speeds. I like to engine break, almost never use the rear brake.
Done just 60k miles on my 2010 GSA on various tyres, Tourance Next, PR4s etc, never got less than 6k from those, not significantly more either if I recall correctly.
Best mileage so far has definitely been on the PR5 Trails, am on my second set, first set changed after 12k, but had some thread left, second set has been in use about 5k, plenty of thread left but I'm probably gonna change the rear at next service due to puncture repair. Probably gonna go with Roadsmart 3 which I liked the feel of better and seemed to me to have almost as good wear.
But it's not like I'm a feather weight or especially gentle.
If I should hazard a guess as to why I get good mileage out tyres its probably because most of the mileage is done on 300-500 mile days where they get to work at operating temps. Use about 33psi front and 44 in the rear, sometimes a psi or two more, never less.