But then the whole disadvantage of being stuck on imperfect Earth and never getting a chance to go onto a potentially better afterlife is gone...

Which is always the downside of being immortal...

But to Digory's mother, the disadvantage seems that it would apply.

Which is why it's a good thing she didn't eat that apple.

~Riella

"That is what would have happened, child, with a stolen apple. It is not what will happen now. What I give you now will bring joy. It will not, in your world, give endless life, but it will heal."

When my dad and I were discussing this during our first reading, we came up with the conclusion that Aslan was saying that it was better to die in this world, and go on to be with God in heaven, then to be stuck living here in this sinful world forever.

Also note that Aslan says endless life, not eternal youth, like the elves in LoTR possess.

Yes it sounds more like what happened to Voldemort than what happened to the LOTR elves. This is the extract from GOF (p. 566 my ed) which was his idea of endless life, and which reminds me so much of Aslan's talk to Digory.

"Aaah...pain beyond pain, my friends; nothing could have prepared me for it..... I was less than spirit, less than the meanest ghost... but still, I was alive. What I was, even I do not know...I, who had gone further than anybody along the path to immortality. You know my goal, to conquer death."

And Dumbledore replies to Voldemort in the following HP book, Order of the Phoenix (p. 718)

"...your failure to understand that there are things much worse than death has always been your greatest weakness".

Whether it is the White Witch or Voldemort the 'endless life' is a corrupt one, full of pain, regret and despair, devoid of joy and happiness, brought about by sinful choices, like trespass, theft and in Voldemort's case, murder. As Aslan would say, death would be preferable.

Isn't that also what was said on the gates of the garden?

Come in by the gate or not at al
Take of my fruit for others or forbear
For those who steal or those who climb my wall
Shall find their heart's desire and find despair.

I think 'eternal life' meant that she would never die of natural causes--never grow old or get sick, but it doesn't necessarily mean that she couldn't be killed. Fiction is full of immortal creatures--like elves--that can still be killed. I think that was what Lewis meant by 'eternal life.'

And now, Stardf29's Lesson on Different Types of "Eternal Life".

"Eternal Life", oftentimes also called "Immortality", can come in many shapes and forms. Here are some of the forms commonly used:

Type 1: Perfect Immortality
Under this type, a being is completely immune to both harm and death in any form. This includes old age, meaning at a certain point, the being stops aging physically. Morgoth from LotR is probably the best example I have that most people here would know of.

Type 2: Biological Immortality
The being will not die from old age, or from other natural causes like disease, but can be killed. This seems to be the type Jadis got by eating that apple.

Type 3: Regenerative Immortality
The being can be attacked, but most injuries, possibly even fatal ones, will be recovered from, due to some special sort of healing factor. Sometimes, this even counteracts aging. Sometimes, there is a special way in order to "kill" such a being.

Type 4: Resurrective Immortality
The being can be attacked and even killed, but if killed, it will simply come back to life. The phoenix is the classic example of this type of immortality.

Type 5: External Immortality
Immortality is conferred, sometimes temporarily, via an external source. In some cases, this involves separating life-force from the body, such that it can be used in a resurrective process should the body be killed. Voldemort is an example of this type of immortality. The actual immortality conferred can overlap with one of the above four.

There are various other types, such as vampiric, undead, parasitic, and "not gonna die because there would be no story otherwise".

Basically, immortality can be categorized by asking the following questions:

1. Can the being die from natural causes, particularly aging?
2. Can the being die from external causes, i.e. fatal injuries?
3. If the being dies, can he/she/it come back to life?

End lesson.