Simple and straightforward:
* The stars will shine for eternity.
* He felt a sense of eternity as he gazed at the vast ocean.
More descriptive:
* The love they shared seemed destined to last for an eternity.
* The inscription on the tombstone read, "For all eternity, your memory will live on."
Figurative language:
* He spent an eternity waiting for the bus to arrive. (Hyperbole)
* Her smile was like a glimpse of eternity. (Metaphor)
Philosophical:
* The question of what happens after eternity is a profound one.
* Some believe that our souls live on for eternity.
Literary:
* "In the vastness of eternity, our lives are but a fleeting moment." (Quote)
* The ancient ruins whispered tales of forgotten civilizations and their long-gone eternity.
Choose the sentence that best fits the context of your writing!