Five years ago when I first starting riding my motorized bicycle it was about thirty miles when I decided to change my chain. I was having to adjust it on every ride.
I commuted to work everyday for five years and three months. (too far to commute today)
Two years ago my throttle cable broke on a very long ride.
This summer on my fifth year and well over 4,000 miles is when I started having trouble. First, I had to replace my rear wheel due to breaking spokes on almost every ride.
Second, my rear mount broke...hmmmm...thats it.
I'm using the same studs...same gaskets...same no bearing chain tensioner. I ran the stock plug and wire for over four years and with no fuel filter. My kill switch lasted three 1/2 years before it fell apart. And I never installed the stock clutch lever just used a brake lever. Still using the stock clutch cable. And I've never had to adjust my clutch.
The only real problems I have had is from my own fault. Like I forgot to tighten my tensioner one time and it got into my spokes. I always seem to forget to bolt my brake arm for my coaster brake and you know what happens when you go to use the brake
So I've had a bent rear sprocket for almost a year now and no chain problems what so ever.
So five years and some 4,400 miles...Chain, kill switch, rear mount, rear wheel, and a throttle cable.
Only once I had to pedal home and that was when my tensioner fell off. Even when my throttle cable broke I still managed to reach my destination with a little road side fix.
Oh, and I have had three flats two in the last couple months.
I also lost my rear brakes comming down a Mountain and almost hit head on to uncomming traffic when I was going to fast to make a turn...I now have front brakes but mostly to make everybody on the forum feel better

I like to live on the edge