I think there are negative correlations with excessive sleep and mortality/health. But I doubt there is causality. As in it is much more likely that people who are of poor mental/physical health will sleep more, rather than your health deteriorating because you are sleeping +1 hour than the accepted norm.

I wouldn't worry too much, it is an absolute blessing that you have the conditions and the body to sustain 9h sleep cycles. As a father of two, with copious amounts of caffeine intake, I wouldn't mind having some nights with that quality of sleep myself! :)