it is hard to predict the future network of a person might have. but someone's key value to an organization is their network -- especially weak ties to other people. obviously, the younger a person is, the more likely s/he is to have massively increased network 20 years from now as people's value grow.
many people go through what i call a "network enhancing event" -- that is some sort of life event/change that massively increases one's network. Like b-school. Harvard Business School is a good example (large, highly social people). One's network can essentially double or triple. most of the people who go to college experience this.
my feeling on the value of college is not much (besides pressures from society and learning how to drink beer). but the network one gains can be extraordinarily important and one can learn a lot.
A "network enhancing event" could be a variety of things. for an academic, it might be writing a well-received paper or book. it might be a job change that forces you to interact w/ tons of people. it might even be gaining a new good friend or significant other that is more social or has access to a different set of people. it might be moving to a new town.
many people go through 2-4 network enhancing events in their lifetime and thus "valuing" someone's network might change over time