I don't ride a lot. 150-200 hours a year usually, which, in the scheme of things, is not a lot. I also try and keep my bike relatively clean.

I buy 3-4 cassettes every few years. If I buy cassettes I want at low retail, they'll set me back $500-600, chains will be $150 for a pair or so. I'd like to get one lighter cassette for my race wheel, a couple medium level cassettes, and the rest whatever I can find.

If I do a bulk buy of (SRAM) derailleurs, (SRAM/Shimano) cassettes, and (SRAM/Shimano) chains, I can get two rear derailleurs, two or more chains, cassettes (6-8 of them), freehub bodies for a few wheels, for about the same amount of money (as the Campy cassettes/chains alone). Heck, some of the cheaper 10s cassettes are under $20 - I can barely buy a cog for a Campy cassette wholesale for that.

For the SRAM/Campy thing I just have to make the change all at once.

If I get some cable pull adjuster then I skip buying the rear derailleurs and use the Campy rear derailleurs I have.

I expect to go through my last good cassette/s this year. I have a Record and a Chorus left, plus the Miche. I have two full-ti cassettes but I don't feel the need to use them up (they're non-Campy, lower quality).

cdr