If something happens sempiternally, it happens forever and ever without stopping.
The word sempiternally makes people think of things that never end, like the sky or the sea.
Examples:
The stars shine sempiternally in the night sky.
She promised to love him sempiternally.
The river flows sempiternally towards the sea.
I could listen to that song sempiternally!
The mountain stood sempiternally, never changing.
The old tree seemed to stand sempiternally in the forest.