Barenia is a beautiful leather, and looks gorgeous in a K or a B, but it will darken, get spots, scratches, etc. Just the nature of the leather, as they say. I think it is a great, super cool-casual, look. It will take on a somewhat distressed appearance, at least more than some other leathers.
If you want something that will transition to dressy, barenia is probably not the leather. I have a Ebene barenia and toile kelly and it is one of my favorite bags, but the barenia definitely has that lived-in look. If you are looking at fauve barenia, it will show spots and darkening more than ebene, and the darkening does not all happen evenly. Again, this is normal and part of the cool and casual feel of the leather.
I'm not sure I would use a barenia bag everyday. I leave box and barenia home on rainy days and grab togo, clemence or buffle skipper, which is super impervious to bad weather.