Originally Posted by cyclezen

really, put the new chain on and take it for a ride - you've got a better than 70% chance (my number...) that the cassette will work fine...

rotating chains - why?
so that you get 3 or 4 chains going south at the same interval? and wearing the cogs more during that time?
just get a chain checker and repalce chains when the .75 mark is reached - you'll get 20K+ miles out of the cassettes, even if you aren;t very diligent in keeping them spotless.
For me it's a choice of maintenance time or riding time - I mainly choose riding...
I WD40 the chain (yes, sad but true.. ) and wipe clean, every 70-80ish miles - about every 2 rides. I'll pull it off and clean it every 800 mi or so... or if I ride in the rain and it's really caked grundge. A KMC DX10sc will give me about 2.5 to 3K mi. Have not replaced a 10 spd cassette yet in 6 years and avging 7k to 9k a yr (half of which is done on some 9 spd machines...) or 25K miles ttl on two10 spd machines...