I've burned through a chain in 2000 miles, and I've had one go 5000 with no defectable wear. So chain life IME is really all over the map. I used to put a drop of tri-flo on every link every 500 miles (about once per month) and one got gummy, attracted dirt, and wore out, the other lasted for ever. I can't explain why. Now, every couple of rides I give the casette a quick spray with WD-40 while running the crank backwards. They appear cleaner and l haven't worn one out yet. As a rule of thumb, I know if they sound squeaky I'm delinquent.

...and I never clean.
YMMV