Bicycle Mechanics - Cassette Wear/Replacement

What is the time tested method of deciding that one's cassette requires replacement?

My story - At the end of last season I replaced a worn-out Campy 10-speed chain (3500 miles - started skipping) and replaced with a new Wipperman Conex. I thoroughly inspected the Campy UD 13-26 cassette and could not detect any excess wear and it shifts very well with the new chain. I have about 1,000 miles on the Wipperman and it and the cassette are both performing admirably.

So, what should I be looking for on the cassette that I may have missed?

BTW, I was happy with the Campy, but want to see if the Wipperman will give me twice the mileage, as advertised. Thanks.

I had a similer problem and these are the answers I received from the helpful Bike forums members.

http://www.bikeforums.net/showthread.php?s=&threadid=23897

I use a mixture of how well it is working, how worn out the chain is and looking at the cassette. Are the teeth staring to sharktooth or get pointy. Comparing to a new one is helpful as well.
If it were a Shimano you could use a Rohloff cass. tool altho my results with that have been iffy, it requires enough "feel" that you might as well do it just by eye.

Go to the lower 1/2 of this page...
http://www.sheldonbrown.com/chains.html

In general, if your chain was allowed to wear out beyond the recommended change point you can expect to find excess wear on the cassette cogs you ride in most often. Also, don't forget about the wear and tear on the chain rings. If the cassette cogs are damaged chances are your chain rings may be showing excess wear too.

On the Wipperman chains, I think you'll be disappointed if you're expecting double the life of a Campy 10sp chain; a 40% improvement is the manufacturer's benchmark and that seems to be consistent with what I've seen and hear from folks who are using them. Moreover, like any chain, to get the max. life from them they need to start off on good cogs and chainrings and receive proper maintenance, i.e., all things being equal the Wipperman should give you ~4,900 mi if you got 3,500 from the Campy chains. However, I'd say the chain rings and cogs are suspect if the chain was already skipping due to excess wear.