In reply to bouldery bits:
Before you first use them give them a couple of coats of the Grangers proofing spray. It helps keep the stains at bay for a long time. Clean them after each use, if you an be bothered, and treat with spray or the Nikwax nubuck and suede proof.
If they start wetting out too quickly, or you cant be bothered with the faff of keeping the nubuck looking good, just polish them with Graingers wax or similar. They'll just look like any other leather boots, and I can't say as I've ever noticed a decrease in breathability in real use.