I get 4,000 miles out of a 10sp chain, give or take. The chain lube du jour is Muc Off Hydrophobic Team Sky Edition, because it routinely lasts 2 weeks between applications (about 500 miles.) Every two months (give or take) I remove the chain and clean it with a scrub brush in the sink with citrus-based cleaner (ProGold or Muc Off) until the water runs (mostly) clear. I then spray the links with brake cleaner until the last of the muck from between the links is gone, and the solvent runs clear.

The chain then goes in the toaster oven for 20 minutes @ 250ºF to remove any residual moisture. Chain lube is usually applied while the chain is still warm, unless I forget the chain in the oven and it cools off. The chain cleaning process generally takes ~30 minutes. When a new chain goes on, the chainrings and cassette are cleaned in the same manner, just no oven to dry. New cassette every two chains.