My chain had 5500 miles on it, and it and cassette are still going strong. Shimano 105 cassette, I think, 9 speed. I took them off, though, to put on a new (Ultegra) cassette, and thus a new chain, with more mountain-y gears. But the mechanic is cleaning the old stuff for me in case I want to put them back on- there's _still_ life in them! And I shift a LOT.

I was worried about chain life, too, because BF replaces his chain at 500 miles!! and had them check it with a chain measuring tool a couple months ago and it was still good.

Nanci