Focus Scripture: 1 Timothy 4:12
What is the significance of someone's age when it comes to the strength of their faith? According to 1 Timothy--it isn't. What is relevant is the believers conduct in faith.
"Don’t let anyone look down on you because you are young, but set an example for the believers in speech, in conduct, in love, in faith and in purity."
It is how we live, how we speak, how we love that will say more about faith than our age. Of course that is easy for me to say--I have "credentials" as a pastor and the benefit of a certain amount of age (51 as of a little over a week ago). But those aren't the kinds of credentials that Paul was interested in.
Paul's point is that what makes someone a Christian to look up to is based on how they live, how well they follow Jesus. That is the truest test of faith and the real strength of faith.