as long as you keep it oiled and clean, the chain will last longer than you might think. i kept one on my 99 sv for 33k miles and i was pretty ruthless on that bike, but always kept the chain clean and serviced. Running it dry, or in dirty situations, or rust for those that leave them outside is the worst you can do to them, but it happens. Just check it every few hundred miles, see where its at. stretch depends on usage and riding style and environment. you'll eventually figure out how many miles it takes to get out of adjustment on YOUR bike. for me, its its over 1/2" total out, i adjust.