Maturity is not wholly dependent on age though they have a link. Making mistakes is part of learning. When a child takes his hand to test the reaction of fire to his skin, he would get hurt the first time. However, when he sees the fire the next time, experience would teach him that touching it is dangerous. Maturity has come to play. This requires time in every sense of it.
There is one adage that says that a child can have clothes like an elder but he can't have rags in equal manner. This is to explain that age has a lot to do with experience and experience has a lot to do with maturity.
The challenge comes from the situation whereby someone refuses to learn as he ages. Providence will make you pass through many stages but not everyone would be able to learn from the process. It is due to the reason that you could see an old person not exhibiting the maturity expected of his age. Such a person has refused to learn from his experiences and become a better person.
The age of 18 is the age of maturity in Nigeria. It is the age where one enjoys the privilege of adulthood. It signifies the age of eligibility for participating in the voting process to elect leaders. It is also the age that makes one qualifies to own a bank account as an adult. In the criminal justice system, it is the age in which one could be sentenced to jail as an adult.
Aside from all these highlighted legal implications of turning 18, I don't see the age as the age of maturity necessarily. Some teenagers of less than 18 could be more mature that someone in his 30s or 40s. To me, the age of maturity varies in individuals.
For one to be mature, you have to possess emotional intelligence. When young people behave immaturely, it is often blamed on their age. It is assumed that they are not emotionally intelligent. A mature person should act in such a way that he is deliberate in all that he does to add value to humanity. If you don't have this quality as a septuagenarian or more, you are not mature. A kid that displays this characteristic is mature.
It is for this reason that some young leaders do better than the older ones. If maturity is strictly a product of age, leaders from older generations would have been the best in delivering quality leadership. It is glaring that this is not the case in Nigeria. I am not denying the instance of having it in the opposite. I mean an old leader could perform wonders while his younger counterparts squandered the goodwill of the people. It's purely not a product of age.
Once a man, no matter how young he is, is able to show emotional intelligence in addition to other intelligent quotients in relating with people or situations, he is mature. Maturity is not a product of age. We can have a mature young man and an immature old man. The direct opposite can also be the case.