I've never gotten more than 2000 miles out of a bushing chain. It's too hard to get lubrication and cleaners into the bushing. If oil drips down into both ends of a bushing, it traps an air-bubble in between them and no more flow occurs.

With bushingless chains, it's much easier for cleaners and lube to get into the parts that wear and I regularly see 4000-8000 miles out of bushingless chain.