Good point, I hadn't thought of that. I was thinking most of the ones that I see use blue ink with no outlines for the tiny tattoos, so I could see those fading significantly in the future. Now that you mention it though, they would all still make good tattoos without the miniature tattoos so it doesn't really matter.
As a bonus, when you run out of room for tattoos, you can get the tattoos on your tattoos tattooed again!