We have to believe the truths that we know. We know that God is all knowing, loving and so on. No matter the judgement, it will be perfect. There was a priest who Maximillan Kloble, who thought, what will happen when there is no limbo, at final judgement. He was of the opinion, that if God asked the angels if they would serve him, would he do the same with those in limbo? We don't always have questions answered. The truths that we do have can help us to come to peace, knowing that God is perfect. Prayers are never wasted. God knows our hearts and when we pray we pray for all those in need. Those in purgatory pray for us and all those in need, and that is an article of Faith and a most consoling one.