Some cockatiels live more than 30 years, so 16 is very very common
I've always known the "average" lifespan to be 12- 14 years. With a nice amount of Cockatiels living to 20- 25years. Occasionally living to 25+, but not often. That's what I always thought, but I could be wrong. I thought 16 was above average for a cockatiel. (Of corse average doesn't mean much when considering the ones the died young lower the average age.)