I wondered the same thing when I first bought this little bike. I now have over 21,000 miles on her (about 5,000 year as mentioned), and this is what I have experienced so far, in terms of "parts replacement"...(in chronological order, as best as I can remember)
4. Rear sprocket and chain
5. Rear brake shoes
6. Front sprocket, rear sprocket and O-ring chain.
7. Both tires
9. Rear brake shoes
8. Stator coil
9. Fork boots
These are the "major" components that I have needed to replace because of breakdowns. I have not included the gallons of oil (I'm a bit of a fanatic when it comes to oil), spark plugs, Stearns seat-covers, rear axle (stripped on account of my stupidity, not an actual "breakdown"), oil and/or fuel filters, hand grips or levers.
It's like they say...the harder you treat it, the more likely you are to break stuff.
I really pamper mine; partly because I want it to last and partly because I'm a big chicken!