I think I will not polish them. I like the un-polished look. They will get darker anyways (which is good).
The complete bike gains lot of style with this patina-thing. Every part on the bike looks so wonderfully antique but still tidy. All the parts fit perfectly together. I think a polished pair of brass-fenders would spoil the dignity of the bike.

I infact didn't test the functionality yet, as it didn't rain for some days. But I took some attention in the lenght of the rear splash guard. Theoretically it should work. I will report as soon as it starts raining.