I'm fifteen and I consider myself mature enough to own an exotic without outside help, although I'm holding off actually purchasing the thing I've been learning about for roughly two years to respect my parent's wishes and because in a few years time I will probably be going off to university where the situation will not be ideal for a ball python, meaning I would have to most likely permanently or temporarily give up one of my most treasured "possessions" so soon after acquiring it. I think that once you've got to a certain age, perhaps the mid-twenties, you are reasonably mature. Otherwise it can vary greatly.

Not naming names, but there have been one or two members here (I have no idea how old they were) that simply were not mature enough to own any sort of pet, as they simply were not responsible enough to do all that is necessary to take good care of it. At times, they didn't even do all that was necessary to keep it breathing.