With proper maintenance the stock chain is good for 15,000 to 20,000 miles. Sprockets should last at least twice as long.
For lubing instructions go to:
www.vincesmotorcyclestore.com/spoke.html#lubing Also, most people run their chains too tight or too loose. Rotate the wheel to find the tightest point on the chain. At this point you should have an inch of actual play, mid way between the sprockets, on the bottom, with you sitting on the bike. This is the way most people ride, so this is where you adjust it.
Cam type adjusters sometimes will put it between tight and loose. Choose the looser adjustment.
Most of my guys get this kind of service from their chain. On my own XS650 my non-oring chain gets 15,000 + MILES. In 115,000 miles I am on my second rear sprocket.
These are easily obtainable goals if you are a little anal about proper maintenance.