I have a yellow banded Possum Wrasse that I have had for about 3 years. Had him for a year in my nano tank, and is now in my 150gallon. Always spent most of his time in the rock work, will come out and display a little in the evenings when the actins are on, and the sun is setting (ambient light hits the one half of my tank).
I have had fun putting a little piece of mirror on the corner of my tank for a few hours every couple of weeks. All the fish will go and display against their reflection, the Possum Wrasse is one of them that really get's into it. He forgets he is suppose to be cryptic and stays out and displays.
As mentioned I don't do this regularly as I don't want to mess with their brain, and create aggression problems in the tank.