My 2¢ on chains,
If you properly maintain your chain, it should last awhile, no really set mileage.
Proper maintenance includes cleaning, lube, and correct adjustments.
I myself use the DuPont Teflon spray, here is a link to review,
http://www.webbikeworld.com/t2/motor...n-chain-saver/
http://www.webbikeworld.com/t2/dupon...ain-lube-2012/
I generally clean and lube my chain about every third tank of fuel, on my Ninja 500 I've managed to get close to 20k miles out of a chain, I replaced it when it started to stretch like crazy.