Well, the necessity of washing chains varies with prevailing conditions. My winter commuter gets it SRAM PC-870 chain boiled once a week whether it wants a bath or not, water being the ONLY thing that can dissolve salt. This also gives me an opportunity to use WD-40 for its only good use, which is displacing water.

Tri-Flow is a pretty acceptable all-around chainlube, though I prefer a foaming moy lube I get through industrial supply sources.

The rule of thumb is that you don't want to run your chain bone-dry, but you don't want it wet enough to pick up grit. I tend to err on the side of wet in the wintertime; I reckon any grit that accumulates will at least be really well-lubricated grit; maybe that helps.

But... yeah. Clean, clean, clean.