I would guess that in the wild, giants like the Napoleon or lumphead wrasse (Cheilinus undulatus) will live much longer than the tiny Wetmorella genus, with a wide range in between.
But I suppose my friend wanted to know how long a wrasse would live in my aquarium. Again I don't really know. If the expected lifespan of the genus I keep is between 5 and 8 years, I have seen this reported on a number of forums, then the age at which a fish is introduced will have some bearing on how long it will live in my aquarium.
I have lost a C. solorensis after three years after he jumped through a tiny gap in the cover and a P. mccoskeri after about 3 years after he injured his jaw.
The oldest resident in my reef at present is a beautiful M bipartitus. She has been with me for 6 years and 2 months.
I do try to buy my fish when they are small juveniles, which I guess would be about 12 to 18 months old. Maybe a little younger, it is hard to tell. If a fish is larger and developing its adult colouration then they are obviously older, maybe up to a couple of years old. An adult super male could be several years old. The older fish will therefore spend less time on my reef.
I have posted images of each of my wrasse with the amount of time they have lived on my reef as of 14.12.2020
I guess the most mature fish I purchased was the C. solorensis. All others were relatively small juveniles.