how many times can you go over old work

I had a tattoo covering the top half of my arm and going over my shoulder, and a band on my forearm. The top half was dated and I wanted some sort of cover up. I went to an artist who was probably a good artist but not tattooist, where we proceeded to cover it with a japenese style sleeve. But I have lost faith now as he has lost interest and it now just looks unfinished. So I really wanted to know how many times can you go over work as some of this has been gone over 6 or more times, either that or i'll consider laser to try and remove as much as i can.

unlimited... as long as the skin is not scarred