Lucky for us, God can do it in an instant.
Perhaps some of the discussion has been derailed by the difference in what God CAN do and what he DID.
I think we all agree that God CAN do anything.
In his revealed Word, he DID only some things. It is my belief that he is SOOOO powerful that he is accomplishing EVERYTHING he wants through the specific things that he did do.
He set laws in our nature that later we found to correspond in his revealed law. He COULD have built us differently, but he didn’t.
I think we have to come to terms with the fact that, out of an infinity of choices, he MADE some of those choices and therefore others are no longer possible if God is to keep his own Word. He cannot, for instance, allow the Church to be prevailed against. He said it wouldn’t be.
Insofar as Purgatory is concerned, we know so little. The Church itself can only pass down what it knows and that may not be enough to satisfy all our questions.
We need to come to terms with the fact that Purgatory is compatible with both God’s mercy and his justice. It is VERY merciful to allow a path for a person who repented but died to enter heaven without violating God’s justice (and his own Words) because the person is still unclean.
In non-Catholic Christianity you have to assume God does something behind-the-scenes to make it all right (cooks the books to make all accounts add up or else tosses the books out). Is that fair or just to those who suffered for the sake of their own and His purity?
Again, I believe God is SO powerful that he does not need to resort to sleight-of-hand. He does it all right in front of us and reveals HOW he does it through his Word (written and unwritten) and we can only marvel at his power and majesty. We can only consent to receive it.
Our God is an AWESOME God!