I just wipe mine with a rag either every couple of hundred miles or after it has got wet, and then put lubricant on it. I also scrape visible dirt off jockey wheels, chainring, etc and wipe cassette with rag. I know I should oil the chain slowly, on each roller but I CBA so I just spin the chain as it squirts on, which takes about 3 seconds.
I used to rotate chains and give them a thorough clean but ended up with dozens of half-eaten chains hanging off nails in the garage and couldn't remember which bike they were from, so don't do that any more. I just run them until they have stretched. I tend to replace them fairly early (c. 1000-1500 km) so don't think I've worn out a cassette in the last 10 years.
I have had gadgets like the park tool one but they always spilled gunk everywhere and broke pretty quickly. I was toying with the idea of buying another, which was why I read this thread, but it has persuaded me not to.