Maturing does not just mean studying the Bible, but getting out and doing the work.  Anyone who believes they can become mature in Christ, simply by learning and not putting what they have learned into practice, deceives themselves.  James 2:17 says, "Faith without works is dead!" 
However, Paul also explains this in Hebrews 5:12-14, "For though by this time you ought to be teachers, you need someone to teach you again the first principles of the oracles of God; and you have come to need milk and not solid food. For everyone who partakes only of milk is unskilled in the word of righteousness, for he is a babe. But solid food belongs to those who are of full age, that is, those who by reason of use have their senses exercised to discern both good and evil."  
A Christian that does not share and demonstrate the gospel, is neither effective nor obedient!  Jesus called us to share the good news of the kingdom, heal the sick, cast out devils, and raise the dead, all while making disciples of all nations.  Freely we have received, freely we should give!