The thing about family is, its relationships are neither temporal nor conditional. If you are the son of your father, you will always be your father’s son. Unlike friendship, citizenship, and work relationships, all of which can cease to be true after a given amount of time, or under certain conditions, family is always true, whether acknowledged or not.
In most religions, membership comes with conditions, and salvation is one or lost based on how well you meet them. But Christianity is different. Christianity is Family. And not just any family, but one with a perfect Father, and a perfect first born Son.
When salvation is granted by a request made in faith, we are born spiritually into this perfect family. We become sons and daughters (Ga 4:6, Ro 8:14). And never, through action or inaction (Ro 8:38-39) can that relationship ever change. It is as immutable as the very word of God Himself (Mt 5:18).
We may play the prodigal, but even whilst the wayward son was frittering away his inheritance (Lu 15:13), he was still his fathers son, and like the prodigal, those of us who use unwisely the gifts we have as the children of God, though we return crying that we are unworthy to be called sons and daughters, always will He take us into His arms and declare that His child has come home (Lu 15:20-24).