Not easy to answer, but I am running >3-4.000km on the rear (Pilot Power CT2 and Pilot Pure CT2), and I guess double on the front.
That is with ~120-140hp depending the bike, a lot of stop and go, and squaring off more then anything else.
I used to change them halfway to my trackbike to use all of them, but hardly any trackdays recently.

You should easily do double the distance with your NK.

By the way, I am not sure on your rim size and the space you have on chain, swingarm and some other obstructing stuff.
But if that allows, there is nothing against trying a 180/55.
You will have a bit more rubber on the road, and the geometry will not be too different, unless you nail it in the corners (which is highly unhealthy in China if you are not on a track).

E.