4-5 seems the average though as most of the time, there are people who would not know how to properly care for these fish but kuhlis do live for a long time. I am sure you provided him the best care that you did, Beezer.:thumbsup:
I heard one time of someone having one for something like 18 years, but I have no idea if that was true or not, definitely not typical. Loaches do tend to be pretty long-lived though.