2013 Geniune Stella 4T
 

anyone venture to guess how many miles one of these would last (taken care of)?

If it is chinese, it's the russian roulette.
The cheaper you buy (new), the cheaper you get.

It is just my personnal opinion but up to a two times price difference, I would favor a used japanese bike (any mileage up to 30K) over a new chinese one.
Chinese @ 1000$ => I would go for a 30K 2000$ japanese bike without an hesitation.

Taiwanese is different.

Genuine=India or Taiwan. Generally quality is on par with Japan with a few quircks to make them interesting.

Contact your local dealer and talk to the service department to see what is typical mileage for ring and piston replacement. Do the same for Aprilia, Honda and Kawasaki 50cc scooters. A Ninja 250cc engine is reported to last around 100k.

For $3700 msrp I'd rather get a used CBR250R, or Ninja 250, or any another Japanese 250. Styling is really good though.

To answer your question, it all depends. If it is maintained really well and not flogged on the freeway most of the time expect 20-30K, maybe more. Some Chinese 200's roll 40-50K with no major work.

Chinese motors are often pretty good. The key to most Chinese bikes is the set-up, break-in and maintenance. Many people don't pay much for them, treat them like crap, break them and say they are crap. Japanese, German and US bikes are also crap if they are treated as such.

Maybe the strategy is becoming "if you pay $3700 for a Chinese scooter you'll take care of it and it will last". Maybe that is how the China bikes will finally get a good reputation.

What do I know? I purchased my current China bike for $160, and it runs and rides great, despite the previous owner taking zero care for it. Call it a rescue bike.