I've owned a '96 since it was new. It now has over 45,000 miles on it. Recently I had to replace the carburetor because some of the internal parts had worn out, and the engine will soon need to be rebuilt. And the front brake rotor wore out.
When the bike was new, I had to have the valve clearance adjusted every 5,000 miles or so, as it would go out of spec very quickly, and the bike would die when the engine got hot. But that problem has gone away over time.
Aside from those things, all I've had to do is normal maintenance. However, I have not used this bike in the dirt at all (unless you count the occasional dirt road). It's been my only transportation for several years now, and I also use it for fun rides in the hills. The longest day I've done on it was about 300 miles, and I didn't find the seat to be uncomfortable at all. I'm probably quite a bit smaller than most people who ride this bike though.