I get about 3,000 miles out of a chain absolute max, no matter what chain, or how it is maintained.

I get about 3 times that out of a cassette.

The expensive approach to drivetrain maintenance is to let your chain wear to 5,000 miles, which will cause your cassette and rings to be eaten away exponentially. Then they will all have to be replaced together - prematurely at 5,000 miles.

Chains are cheap; replace often. Please do it 'donate' worn-out useless chains to your local bike Co-op. Throw them away; they are inanimate objects without feelings or a soul. They are trash; get over it.