When Time is recognized as part of A Being, then we can also understand how a Being can remain the same Being - even if/when its component elements are all replaced.
And we can also understand that when an entity is not a Being, and its component parts are all replaced - then what results is no longer the same thing as it was to start with.
This is the Ship of Theseus paradox from philosophy; but it is more clearly stated by the simpler example of contrasting Geordie the Man, and Geordie's hammer.
If we suppose that over the course of fifty years every cell in Geordie's body has been replaced (which isn't really true, because some nerve and muscle cells are preserved through the lifespan; but let's assume it)...
Then, despite that none of his component parts remain from fifty years before - we nonetheless regard Geordie as The Same Person as he was fifty years earlier.
Whereas, by contrast, we regard Geordie's hammer - which has had three new iron heads and twelve new wooden handles during the fifty years - as Not the same hammer as it was before (even if the replacement heads and handles are always shaped identically to the original).
Why the difference between Geordie and his hammer?
Why is the Man regarded as being the same, even if his components are changed, even though he has transformed from child to youth, from young man to old man? Whereas the hammer, which looks and functions identically throughout, is nonetheless a different hammer?
The difference is that Geordie is a Being, and the hammer is not.
It is of the nature of Beings that their identity remains, despite whatever repairs, growth, development and transformation that Being has undergone through time - indeed self-repair, growth, development and transformation are actually attributes of a Being.
Indeed Beings are always changing, they are dynamic; which is one way we recognize they are indeed Beings.
Being-ness is thus continuous, it never ceases even for a moment.
There is no paradox here - unless we start assuming that Time can be excluded from our understanding, and/or assuming that Time can be discontinuous (i.e. can stop, and start again - which is another way of assuming that Time can be excluded from the understanding).
If we try to understand Beingness without reference to Time and continuity, then we are driven to assume that Beingness depends on some unchanged essence.
If Beingness were wholly material, that would mean that Geordie was no longer himself when all his component parts had been replaced.
One traditional attempted-solution of this difficulty is to posit an unchanging immaterial spirit, which persists as such even when the body is destroyed, and despite that the soul may change through time (for example, by learning from experience).
But to say that the real Geordie is something eternal and unchanging, is to render all change to body and soul superficial and irrelevant in a context of eternity. This is to posit a reality in which the eternal essences of all Beings - including all Men - are unchanging.
And this is (I believe) contradictory to the whole basis of Christianity; which assumes agency, and that our choices matter fundamentally and eternally+.
(+This tends to lead back to a non-Christian oneness spirituality - where all of reality is assumed to be unified, perfect, unchanging - and all else is illusory. There is no space in such a scheme for God, Jesus or Men as free agents - since all categories entail division, and are thus regarded as ultimately illusory.)
What of Geordie's hammer? Since the hammer is not a Being - what is it?
I would say the hammer - as a separable entity with meaning - is a component of Geordie's Being, a part of Geordie's Being.
The hammer gets meaning from Geordie; but might also be shared by Geordie's friends; or given to another Man (or other Being) - and then would get a somewhat different meaning by becoming part of a different identity.
In general; not every 'thing' is a Being; and those that are not Beings will get their identity - will be recognizable and understandable and have purpose - from their association with one or many Beings: through being known by other Beings.
Therefore; if it was possible that Geordie's hammer ceased to be known by any Being (even God) it would simply become assimilated into 'chaos'; that meaningless, purposeless stuff about which nothing can be said (because as soon as something is said of it - it ceases to be chaos).
The un-known hammer - since it is not a Being - would cease to be a part of divine creation.
(But this presumably does not happen, because God - having known the hammer, would always know the hammer.)
Whereas a Being is known to itself, since consciousness (of some kind) is an attribute of Being (other attributes are Life, Purpose, Change*).
Hence Beings are eternal.
Even if (as was originally the case, before creation) a Being was unknown to God and had not (or not yet) been included in divine creation, it would nonetheless still continue to be.
What all this tells me, is that we should be care-full about how we talk and think about Time - if we wish to avoid incoherence.
If we start separating Time from Beings (and Being-ness), and start assuming that Time can stop, or is discontinuous; then we create paradoxes when it comes to Being.
An analogous problem is Zeno's paradox of the Achilles and the tortoise; this incoherence derives from assuming that Time can be understood as discontinuous, and can be broken into discrete segments.
Similarly; when we try to understand Being, we will run into paradoxes if we try to understand Being in a Time-less fashion.
But if instead we regard Being as a primary aspect of ultimate reality; and recognize that Time is an attribute of Being - then there is no paradox.
Then Being is understandable using ordinary, innate common sense - something even a child knows, without needing to be told.
**
Note: Being is here regarded as a primary category - therefore "A Being" does not, cannot, have a definition. Anything that has a definition is not primary, since it can be further broken down. But Being does have attributes.