The first point I think is that the needs of the gameplay are more important than the lore, otherwise it would be a book, not a game.
The second point I propose is to introduce this stable way of increasing lifespan as a temporary mechanic until you finish the game and in the full version of the game open it only at the peak (if your last stage does not have an infinite lifespan), so it will not break the need for a reasonable speed of development in the early stages, if this is so contrary to your plan for developing the lore.