You will come to your grave at a full age

"You will die at a very old age"

like a stack of grain bundles that goes up at its time

You may need to make explicit that the grain in this simile is fully ripe but not overly ripe. He would neither die young nor become weak in his old age. (See: rc://en/ta/man/translate/figs-explicit and rc://en/ta/man/translate/figs-simile)