It really depends how you define "mature," and the people on your ship as well. Maturity is very much a relative perspective. You'll always have some immature people... it's almost a fact of life. Maturity is really not something that comes easily... age is one of the few factors that does impart maturity.
You'll find some people are more mature, you'll find that others are less. Typically, the more mature types are generally more independent of their parents as well.
Just a few thoughts.