When I'm going to be riding in wet conditions I use Finish Line Wet lube. It's pretty thick and doesn't wash away. On my commuter that usually keeps it quiet for a few weeks. I don't wipe it down until it starts to get noisy or feel sluggish. With this routine I get about 2500 miles out of a chain.
I also use Finish Line Wet for CX racing, but those races are usually pretty muddy and so I end up washing it and relubing after every race. I don't track mileage meticulously in those conditions, but I'd guess those chains don't see 500 miles.
I use a chain checker tool and replace it when it gets to the 0.1% indicator.