I come from a family of tattoo artists, and tattoed people. I would be really wary of any artist who advertised themselves as a finger specialist, or assured you that a finger tattoo wouldn't fade.
For all the reasons stated above, tats on fingers will fade really fast, as well as spread out and blur. The skin on your fingers is very thin, is used and exposed a lot, and regenerates quickly.
Also, any words need to be well placed and spaced so that you won't lose the lettering quickly over time. My father has had our names tattoed on his arms in a few places over the last forty years, and only we know where they are now. I love that he did it, more than once, but it didn't last very long on his sailor's weathered arms.