I never thought about the tarnish aspect.

With copper I'm not worrying about sparkle. I want it to be subdued as I use it only to suggest segmentation or to hold materials in place, so tarnish as I see it is a good thing. If i want it to contrast such as in some midge patterns, I'll use the Uni or other fly tiers wire in silver or gold. I'm also not worried about how my flies look as they are for me...just as long as they work better than the guys next to me.