Others reach spiritual adulthood in just a few years. We have all seen new Christians who have been believers for only a few months outstrip others who have been Christians for decades. All along the highway Christians are pegged by God for their progress toward their destination of maturity. If a baby does not increase in weight and length after a few weeks, something stunts its growth. Lack of nourishment is likely the cause.
Christians stunt their growth due to lack of subsistence.
They may not know the grace of Christ. Growth into maturity takes a regular diet of the unadulterated Word of God. A mature person is a person who has grown up spiritually. We all know aged Christians who think like children and act like children. There are people who have been Christians for 25 years and they still think like a child.