I believe that age has very little to do with maturity. Ones experiences and how a person was raised would probable play a more important role. Reason I say this is because of the different people I've had the pleasure of meeting. Some who have been younger seemed to be more mature than some of those I know who are much older than me. (I have a relative 12 yrs senior that refuses to grow up. I've got the Toys R' Us jingle in my head now )
One could argue that swinging could add to a youngsters life experience. Therefore adding to their maturity. Whether a person allows them to gain this experience is up to them.