Ya derbis have/get the longest belt life too,
Most of my personal puch bikes have 20k or more mi on them (with maintance) some stock, some had major work early on like if the engine was locked up when I got it,
I had a tomoses that had over 11,000 miles on the clock completely original untouched that still ran when I sold them, had Italian bikes with 12,000 original miles on them still ran before I sold them ,
I got a 86 derbi sport and even older electros that have 7k +on them that haven’t been used for 20 years that will start when you put gas in the plug holes so the engines are probably good but cables, controls, carb, tires and everything else is shot so they need restoration but engines, belts and drivetrain are all fine,
Follow your service manual on your bike change fluids lube and adjust everything accordingly, Check and replace rings about 5000 miles, put a piston and rings at 10,000 mi then just rings again (more frequency if single ring and or high rpm set up) and you could get good service life with no loss of performance instead of waiting for the whole top end to wear out and you could get a lot of miles out of a moped, even if it’s kitted!