I don't like disposing of more things than necessary, but replacing a chain is so much easier than cleaning it. A worn chain wears out cogs in the cassette, and it's hard to know just how worn a chain is. Erring on the side of too soon ensures that I'm not endangering my cogs.

I generally buy KMC chains because they seem good and they're less expensive than other brands. So far, so good. SRAM chains were on sale a while back, so I bought about three of them.

The chain collects more dirt than anything else, so preventing it from getting too dirty prevents grime everywhere else.