Hell has often been described as fire, so any scene showing hell as a lake of fire is consistent with the terminology which has been used.
Would I describe it that way? Well…
Until the resurrection of the body, the only thing in hell would be the soul. Fire affects bodies. If the body is not there, then there must be a reason for describing hell as fire, other than the literal. It is an oxymoron to say that fire (flames with heat) can impact the soul as fire is a physical thing and the soul is not.
So why do we find the concept of fire going back 3,000 or more years?
Being burned is an extremely painful matter. Come in contact with a hot stove, etc. and that issue will be well settled. And 3,000 years ago there were not a lot of effective means of treating the pain of a burn, let alone avoiding issues of infections and gangrene. It was, in short, a seriously nasty way to die.
Children are generally not well schooled in psychology at the age of the visionaries, and had Mary given a long treatise on the psychological pain of being cut off from the Beatific Vision, I suspect that not only would the children not be impacted (with/by) holy fear, but likely would not be able to reiterate what they had been told.
In short, it was consistent with images from both the Old and New Testament and was effective and age/education appropriate.
As to Lucia: a) we don’t have a tape recording of Mary’s actual words. it is entirely possible that Mary indicating a “long time” or a “very long time” or even said “Until the end of time”.
For starters, go back to my first paragraph; until the resurrection of the body… So what is time to a spirit? Time is a measure of change; and most people, if they sit down and think a bit, can tell you of instances where time seemed to drag out far in excess of what we might refer to as “clock time”, and other instances where time seemed to “fly by”. We simply do not know what happens on the other side of the veil. But one can likely be safe in betting that once one is dead, if one is in purgatory, that it will be very different from being here enfleshed on earth, if for no other reason than that one no longer has a body.
So in essence, it - Mary’s alleged statement - has little meaning which can be conveyed other than through reference to our senses. Mary is trying to convey a concept, not a “fact” (as in, how many years). My response would be to go back to a biblical saying: To whom much is given, much is demanded. I have no ability to to assess Amelia, either in what she was given (the visions and anything else) nor what sins and/or failings she might have committed, nor why “a long time” might be appropriate for Amelia.
Purgatory is an absolute guarantee we are going to heaven. As it appears that we need to undergo change, that whatever imperfections we have in our person need to be purged, it likely will not be a fun trip, to put it mildly. But it is a guaranteed one-way ticket to heaven. Our purging may be realtively easy; or it may be horrendously difficult, but it comes with more than a promise. It comes with a 24 carat guarantee. So there is phenomenal hope for us.