I've read the other "stretched chain" posts here. I realise the 'stretch' is actually wear, mostly due to road grit, so I clean my road chain once a week with degreaser & the roller brush thingy. I lube it maybe twice a week.
I've tried mixing chains, cassettes and chainrings of various ages before. It seems to me anything less than a brand new chain with a new cassette just aint worth the trouble in terms of noise and slipping. I use a Durace 9spd chain with Ultegra cassette and softer/cheaper Ultegra rings. At the first slip (usually on chainring?), I throw the lot away and start again...even tho there might be a little life left on the chainrings (backwards?). I get about 10 000-14 000miles per assembly doing this...depending on weather.
QUESTION: If I start checking my chain length and throwing away Durace chains (2/3 cost of cassette) which might otherwise last 2-3 times longer before major failure, am I really going to save money on cassettes and chainrings in the long run? Will the new chain really mesh quietly and smoothly with the 1-2 month old cassette?