The eight things do not undergo actual perishing, but their perishing remains possible. Allah could make them perish if He willed, even though He will not make them perish.
By contrast, Allah is subject to neither actual nor possible extinction. The possibility of perishing does not apply to His essence at all.
Therefore, their preservation by Allah does not make them partners in His inherent everlastingness. Allah’s permanence is inherent; theirs depends upon His will.