It is a difficult question to answer, I think there are as many answers as there are people. Some will have similar answers, as a group people may be able to come together and find a purpose that fills the group idea, but will it ever really fit the individual idea. Each persons has a different purpose in their life it seems. For some it is seeking love, money, health, power; for others it is seeking revenge, violence, that which is held by others. 

Purpose and Meaning to me are two divergent things and are not necessarily the same, and defining either of them for self is not an easy thing to do, and as you mentioned will change over time as we grow in our life and our thought processes, and as new information is gathered.