Do you know if you had a tendency to hold it a long time when you were younger? Its possible that the muscles around your bladder are stronger than most, its stretchier than most or a bit less sensitive. I wouldn't overly worry about it. So long as you're drinking enough.
The only reason I'd be concerned is if you were doing a lot of excercise and sweating a lot out, in which case, you might not be drinking enough.