Fortunately, as an Alchemist, Davis had bought many ingredients in sealed containers in the past, so he had thousands of empty jade containers to seal of the potency of these poisonous herbs.
He could seal the herbs for thousands of years and have them not rot or lose any efficiency for over about a thousand years. As for making them not lose efficiency after a thousand years, he would have to place them in Sky Grade containers.
The Earth Grade containers he possessed could only protect and stop leakage from Earth Grade Herbs. With time, the containers would gradually be unable to contain the efficiency and instead, start to decompose from the potency of the energy contained.
They would then start to leak energy before turning useless.
Hence...