Umm, I guess I’m confused here: If angels were created at the dawn of time, and do not reproduce, and no new ones are created, doesn’t that mean that there is a finite number of angels? And since humans reproduce, there is potentially an infinite supply of human souls (or at least, they would outnumber the angels by several orders of magnitude.)
There`s an infinite difference between infinity and a finite number, no matter how huge the finite number is.
I’m no mathematician, but I think logic would dictate that when a person dies, his guardian angel would get a new assignment, just based on the sheer numbers.
Don
t forget that an angel is "only" pure spirit. A spirit consists of intellect and will; and doesnt occupy space. So, there`s no problem with crowding.

Anyway, “Nothing is impossible to God.”: as the archangel Gabriel said to Mary.
i
m pretty sure that the Church teaches that each guardian angel has only one (human) person to look after, and so, doesnt get another one when his particular charge dies. In any case, an angel experiences a different sort of time from the type that a material created being experiences. A created spirit can
t undergo change in substance; but can undergo change of operation: eg. as Gabriel experienced when "sent" to Mary. In other words, time doesnt flow continuously, as it does for matter (which is constantly changing). And time doesn
t drag, either; so there are no angels bored to death and twiddling their thumbs......for a start, they dont have any! They wallow in the Vision of God.
A popular view (Is this taught by the Church?: i don`t remember.) of the fall of the angels is that 1/3 fell, based on Rev 12:3,4: “And another portent appeared in heaven; behold, a great red dragon…His tail swept down a third if the stars of heaven, and cast them to the earth.”. RSV-Catholic Edition. (The dragon is, of course, Satan.)
One belief is that the number of human beings who ultimately reach Heaven is equal to the number of angels who rebelled and fell (and became demons). An inconceivable number for us!
Whatever…but, huge numbers mean nothing to God…
How many subatomic particles are there in the Universe? God knows about all of them because He wills them into existence, and wills their continued existence. A bit simplistic from a scientific viewpoint, but…
This became too longwinded…! Sorry!
I finally picked up a copy of the current catechism just yesterday, and haven’t read through anything yet about angels. I’m still trying to figure out its layout!
Best of luck! i purchased one years ago; and gave up on that quest.
The layout must have been designed by the proverbial committee.
…I hope he got some compensation for that!
He will when your soul joins him in Heaven.