Well here's a way to cut down on the competition: have the kids die.

Sure, the competition is decreased, but so are the chances of the species survival if the environment changes for the worst... that species will have less variety and potentially beneficial adaptations to survive radical change in environment.

So the question is, does natural selection favor the species that bets on one horse or many, which is more likely to be a successful strategy? It's not that the species picks it or plans it, its just the way selection works.

Strong selection environments will favor species that age and die once they have performed their reproductive duties unless there is some beneficial aspect of having them around for longer.

More complex and social species that provide added benefit will tend to live longer as a result because selection will favor lines that don't age and die as quickly if the survival benefit of being around longer is significant.

In other words, you haven't explained aging.

The purpose of the post was hardly intended to be an exhaustive discourse on evolutionary biology. The discussion was around how feasible immortality is given that reproduction is taking place....

Two questions that come up when evaluating the biblical account of Adam and Eve in the garden of Eden before the fall.

The "argument" as you see it is hardly along the lines you are pursuing.

If I use the word "purpose" its simply for easier readability to a wider audience.

I don't think creatures aim to evolve.

Correct, none do but those that do have a better chance of survival in a changing environment.