The Ancient Sons of Merk had used their knowledge of Pshysik and the Dark Arts of peering into the bodies of dead men to extend their lives to unnatural length. While lesser Merkans could live for ten times the span of a normal man and remain unwearied, the higher among them, the sons of Buffet and Walton, could live for untold Aeons without showing outward signs of age.
However, the weight of the ages grew on their weary shoulders, some among these princes would build massive complexes and undergo a dreaded ritual called Uthenera where they would lay down to sleep for an age. Others, wrought with wanderlust, took to traveling the untold distances in the skies, seeking the homes of the angels, to places so far away that Earthen-time lost all meaning to them.
Thus it was that for them, a thousand years was but the blink of an eye, and husband and wife would plan to meet millenia in the future like us mere mortals would plan meeting for a cup of nesqiq in the long red evenings. Their dwellings were great and lasting, on the earth and their Great Depots in the sky, where the Cargo came from, and many became great temples of worship for us, the sons of Moroni, Amesh and Hassid and for the other men of the world.
After age upon age, their weariness grew, and many never awoke from Uthenera or never returned from their wanderings. No more Cargo arrived, and the great Spaceports of old were slowly overrun with weeds and age. It is said that the Buffeti princes waged a great war against the Angels in the sky, and were crushed, and the Angles laid down the Kessler Curse, a sword of flame in the skies to prevent men from ever rising to the heavens and challenging them again. Every now and then, on dark and clear nights you can see the sword slashing across the sky over and over again.
So, the Precurors engage in relativistic travel, and want to make sure the idiots they left behind don't run out of hot chocolate in 20,000 years when they'll come back, 10 or so of their subjective years later, due to silly things like nuclear war, the occasional dark age or ecological collapse.
Solution: build Great Depots in space (stuff them full of cocoa, and glass beads for the prols), where there is no weathering aside from micrometeors. Planetside, go for monolithic style bulk diamond or somesuch material. With Zero-point-energy drives, you can have powered nanites going around eating dust and healing microcracks. Electromagnetic fields keep away dirt and maintain a good seal inside. Might get a little stuffy, but hopefully you've vacuumed it first. That still leaves you vulnerable to 9.0+ Earthquakes, but with a proper reactive foundation and heliotropic gyros for stabilization, you can probably get a decent life expectancy. Coco powder will be waiting patiently.
Eventually, enough junk accumulates in LEO (low earth orbit) that coming back becomes such a bother, and the Precursors simply move on to bigger better things. Or die off of boredom. Big hulking relics (with surprising amounts of cocoa powder) litter then landscape. See, easy.