Both, ChinaV and Chinabiker (Andy) deserve our respect for their 1K-km-trips.
Awesome!!!
ChinaV because he made his trip in a more densely populated area, which required more stops and a lower average speed, therefore more concentration then usually. And: He made it alone.

Andy rode through chilling temps, that's very, very tough, even with heated grips and good gears (ball heater, build-in coffee injection???). The road conditions with snow and ice also require a lot of concentration, you guys must have been pretty exhausted at the end.

I have never made (I never dared to) make such long trips on a bike in China. Even 1k-km-trips in a car in China aren't easy. Or 1k-km-trip on a bike on the German Autobahn can be very exhausting (keeping the average sppeed above 200 km/h ;-). But with a bike in China: WOW!!!!!!

So, what's the next highlight? 1.5K-km or 2K-km...?
Maybe possible in the western porvinces, around Urumqi or Kashgar where the roads are empty, new and flat and during long summer days? Hhm... the frequent police checkpoints in these regions might be a problem for the necessary average speed.
Provided that the sun is up for 18 hours (approx. 15 hours riding) you have to ride with an average speed of 100km/h to complete 1500 km.
That would be like a cannonball race...
Possible? I'll gladly take the bets!