I had one for 3 years until I squished her when moving rocks around after she went under the sand :[. Really stupid on my part. She was a great fish and strikingly beautiful.
My first attempt to keep two together went very well, but another fish killed the male of the pair (and I had that radiant for a year). So after removing the aggressive fish, I moved a smaller male radiant wrasse I had in a 40g to the tank with the single female in it, thinking it would be fine. She responded very aggressively and the little male was dead within minutes. I had the smaller male for about 6 months in the other tank and he was doing well previously.
I haven't had any mysterious deaths with these fish, and I got all of them from the same LFS. I know a lot of other people have though, so be careful with purchasing one.
My big male was huge, and I bought him that size. He decimated my shrimp population... Ate all 5 of my cleaner shrimp, but he was worth it. He was my favorite. He didn't eat my coral banded shrimp, though.
Some pics of the big male.
Size difference between him and the girl when she was still small.