I believe they are from the same family as goldfish, and goldfish have great longevity. I'd be interested in knowing too as I have a barb in my tank...
I need more actually. I need to add at least 3 more GTBs (hopefully males) and 2-3 kuhlis. I know it'll be a little overstocked, but I feel bad watching my GTB school with white clouds (she also looks perpetually pregnant), and my kuhli sulks behind the filter with the other loach...