Why would God desert someone to the far corners of purgatory and let them there for eons of time just because they have no one to pay or pray them out?
Well, first of all we do not know how long people are there so it’s hard to entertain that notion. I think a better question is why do we constantly turn our backs on God when we know better? Honestly, a person you are describing spending decades in purgatory was, theoretically, a very worldly Christian. He or she very likely knew the ways of the Lord yet did not battle sin, they let sin control them and left here with a ton of baggage. They should be thrilled at the fact that heaven is even a possibility, imo.
If I were to believe purgatory exists I would have to have faith that God is in control of my time there and He alone would determine when my soul was made worthy of entrance into heaven.
Understood, let me just say that protestants sometimes at least sort of believe in it as well. My former Anglican minister describes the judgement it as a “painful day” that he is not looking forward to. I’ve heard John Hagee say that if you were a worldly Christian(wood, hay and stubble) then you are going to have a nasty stench in heaven and everybody will know about it. Luther says we are dung covered in snow so no need for purgation. And so what the Catholic Church says is that nothing unclean will enter heaven . No dirty smells and no ‘dung’ either… Revelation 21:27
Remember our Lord’s teachings on persistent prayer like the unjust judge and persistent widow. I think we can effect our happenings here in this life through praying and this continues onto the next life through the communion of saints. If a soul’s time is shortened in purgatory, it is, ultimately, still by God’s great grace and mercy.
God bless you.