Very reliable sled. There are a couple of potential issues that commonly occur.
1. The main wiring harness that goes under the motor over time will chafe through and cause electrical gremlins. For preventative maintenance, wrap it in split plastic wire loom.
2. If ridden hard or not set up properly, the front arm in the rear suspension will crack along the welds. Take it out and inspect for cracks and get it rewelded or reinforced.
3. Premature slider wear always comes up. depending on how the skid is set up it may wear at the front in the bend in the rails or at the rear. Do not panic and change sliders too early as they tend to wear to a point rapidly and then last a long time. To check them take a 10mm open end wrench and try and slip it over the side of the slider. If it slips over it is time to change the slides.
4. On some the water pump impeller seal will develop a leak. If you notice a small amount of coolant at the front of the motor below the exhaust manifold it is probably the water pump seal. It is a simple fix but requires disassembly.
5. The OEM Yokohama track is not a very aggressive track. If in need of a track, you can't go wrong with a 1" six pitch track for all around performance. The sx's don't have a lot of clearance for deep lug tracks but you can go with a 1.25" if not studding.
That is all that comes to mind. Clean the carbs every season and store it properly by stabilizing the fuel and fogging the motor and it will last a long time.
There is a ton of information here in the forums and in the tech pages. Use the search function and have fun.