The reason they supply all those replacement parts is not because they fail promptly and need replacing. Rather, it is because the greatest majority of these tractors are sold in China to farmers in rural areas where it may take several weeks to get parts and they can't afford that time during the growing/harvesting season, nor do they have local dealers for service work. Those parts allow virtually a complete engine rebuild (in the 2 cylinder days it did) without needing to order parts from afar. I believe I read somewhere that this supply of parts is a government mandate for tractors sold domestically (in China, that is), and they just go ahead and send them over here, too.
Can you imagine the response you'd get if you suggested to J-D, New Holland or Case that do something similar?
When these tractors are properly set up and prepped by either the dealer or the initial owner, and given even moderate maintenance, they are sturdy little workhorses that provide a great value for the money. If you get one from a good dealer like Affordable, Ranch Hand, Artrack and a couple of others, all this is done for you and you aren't too likely to have any more problems than you might with most any piece of equipment. I'd have to say that you actually get more than you pay for with most of these Chinese tractors.