Am i immature for still believing aliens might exist when I'm 24?

How old you are has nothing to do with whether you believe in aliens or not. It has never been proven that aliens do or do not exist. It seems like the universe is vast and has an infinite number of stars so there has to be an abundance of alien life out there. We still need to advance more before we can start finding out the answers to this question. Look at how we have advanced technologically in the past 150 years and the pace of advancement is increasing. In another 150 years we may be able to travel efficiently through the galaxy to find out.