Touch Cover Issue

I have a black Touch Cover, and I've only had it for two days. I've noticed discoloration (fading) occurring from usage on the mouse pad, space bar, and a couple of other keys. My concern is the fact that I've been using it for only two days. At this rate, I'd hate to see it after two months. It's not really bad [yet], but it's enough to be noticeable.

I've already talked with Microsoft and they're sending me a replacement. They said it was an isolated issue, but I'm curious as to what you guys have experienced. Maybe I'm being too particular, which wouldn't surprise me...

Thanks!